Pump-detection resonance spectrum based on electron beam

Abstract

A method for time-resolved pump-probe resonance spectroscopy, comprising the steps of:-exposing a sample (4) to a radio frequency pump pulse (20), where the radio frequency pump pulse (20) drives a resonance, where the resonance is electron spin resonance and / or nuclear magnetic resonance, where the sample (4) is located within a magnetic bias field (22); -detecting the sample (4) with an electron detection beam (7) from the electron source (6); detecting a detection beam characteristic of the electron detection beam (7) by means of a detector unit (8), the detection beam characteristic being dependent on a magnetic moment (25) of the sample (4), the magnetic moment (25) being dependent on the driven resonance, the detector unit (8) being configured to detect the detection beam characteristic of the electron detection beam (7) at a temporal resolution for time-resolved detection of the driven resonance; and determining a property of the resonance, in particular a state of the resonance, preferably a change in the state of the resonance, on the basis of the detected probe beam property.

Description

Technical Field

[0001] This invention relates to resonance spectroscopy in conjunction with electron microscopy, particularly spin resonance spectroscopy or magnetic resonance spectroscopy. Specifically, this invention relates to a method for time-resolved pump-probe resonance spectroscopy, and an electron microscope for time-resolved pump-probe resonance spectroscopy, particularly a holographic transmission electron microscope or a ptychography transmission electron microscope. Background Technology

[0002] Electron microscopy, especially transmission electron microscopy (TEM) and its various advanced techniques, such as aberration correction or frozen sample preparation, is a highly developed technology that utilizes the wave properties of electrons to resolve atomic-level structures. The development of fast direct electron detectors (e.g., see X. Llopart, J. Alozy, R. Ballabriga, M. Campbell, R. Casanova, V. Gromov, E. Heijne, T. Poikela, E. Santin, V. Sriskaran, et al., Timepix4, a large area pixel detector readout chip providing sub-200 pstimestamp binning, Journal of Instrumentation 17 (01), C01044, (2022)) and ultrafast transmission electron microscopy has pioneered research processes that simultaneously achieve atomic-scale spatial resolution and sub-picosecond temporal resolution (e.g., see VA Lobastov, R. Srinivasan, and AH Zewail, Four-dimensional ultrafast electron microscopy, Proceedings of the National Academy of Sciences 102, 7069 (2005); And AH Zewail, 4D ultrafast electron diffraction, crystallography, and microscopy (Annual Review of Physical Chemistry 57, 65 (2006)), even utilizing specially optimized interferometric apparatus (e.g., see F. Houdellier, GM Caruso, S. Weber, MJ Hytch, C. Gatel, and A.Arbouet, Optimization of off-axis electronholography performed with femtosecond electron pulses, *Ultramicroscopy* 202, 26 (2019); and A. Arbouet, GM Caruso, and F. Houdellier, Ultrafast transmission electron microscopy: historical development, instrumentation, and applications, *Advances in Imaging and Electron Physics* 207, 1 (2018); and A. Feist, N. Bach, N. Rubiano da Silva, T. Danz, M. Möller, KE Priebe, T. Domröse, JG Gatzmann, S. Rost, J. Schauss, S. Strauch, R. Bormann, M. Sivis, S. Schäfer, and C. Ropers, Ultrafast transmission electron microscopy using a Laser-driven field emitter: Femtosecond resolution with a high coherence electron beam (Ultrafast transmission electron microscopy using a laser-driven field emitter: Femtosecond resolution with a high coherence electron beam), Ultramicroscopy 176, 63 (2017). These ultrafast pump-probe experiments are based on laser-triggered sample excitation (UV-IR), followed by high-temporal-resolution electron detection.

[0003] Resonance spectroscopy, particularly spin resonance or magnetic resonance spectroscopy techniques such as nuclear magnetic resonance (NMR) and electron spin resonance (ESR), is a non-invasive spectroscopic (imaging) technique that has revolutionized not only medical diagnostics, biology, and chemistry, but also brought about a revolutionary change in high-precision measurements in fundamental physics. Furthermore, this technology is used to characterize electrode materials for electrochemical energy storage, which is crucial for addressing the challenges of the renewable energy transition.

[0004] Spin or magnetic resonance spectroscopy and transmission electron microscopy complement each other, providing different insights into structure, materials, and chemical processes. While magnetic resonance spectroscopy is generally non-invasive and offers excellent spectral resolution, electron microscopy offers higher spatial resolution. However, to date, no single technique has been able to simultaneously provide the advantages and insights of both transmission electron microscopy and spin or magnetic resonance spectroscopy.

[0005] JPH09281063A demonstrates a magnetic resonance electron microscope suitable for observing the magnetization state of magnetic materials even when magnetic fields coexist, without being affected by the magnetic field.

[0006] CN 110231354 A discloses a non-laser-excited four-dimensional transmission electron microscope device. The device's built-in excitation mechanism applies non-laser excitation methods to the sample, including DC pulses, radio frequency pulses, thermal pulses, or mechanical force pulses. A high-speed camera records the dynamic changes of the sample. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide a method for time-resolved pump-probe resonance spectroscopy and an electron microscope for time-resolved pump-probe resonance spectroscopy, which can achieve high spectral, high temporal and high spatial resolution (spin) resonances of samples, especially magnetic resonances.

[0008] This objective is achieved through a time-resolved pump-probe resonance spectroscopy method, comprising the following steps: - The sample is exposed to a radio frequency pump pulse, wherein the radio frequency pump pulse drives the resonance of the sample, the resonance being an electron spin resonance and / or a nuclear magnetic resonance, and the sample is in a magnetic bias field; - The sample is probed using an electron probe beam from an electron source; - A detector unit is used to detect the probe beam characteristics of an electron probe beam, wherein the probe beam characteristics depend on the magnetic moment of the sample, and the magnetic moment depends on the driven resonance; the detector unit is configured to detect the probe beam characteristics of the electron probe beam with time resolution, so as to perform time-resolved detection of the driven resonance; and - Based on the detected characteristics of the probe beam, determine the characteristics of the resonance, especially the state of the resonance, preferably the changes in the state of the resonance.

[0009] Furthermore, this objective is achieved through electron microscopy for time-resolved pump-probe resonance spectroscopy, particularly holographic transmission electron microscopy or stacked imaging transmission electron microscopy, which includes: - A sample holder used to support the sample; - A radio frequency pump pulse generator for generating radio frequency pump pulses to drive resonances, particularly spin resonances and / or magnetic resonances, in a sample; wherein the resonances are electronic spin resonances and / or nuclear magnetic resonances; A magnetic bias field generator is used to generate a magnetic bias field to bias the sample. - An electron source used to irradiate a sample with an electron probe beam; - A detector unit for detecting probe beam characteristics of an electron probe beam, particularly phase shift and / or deflection, wherein the probe beam characteristics depend on the magnetic moment of the sample, wherein the magnetic moment depends on the driven resonance, wherein the detector unit is configured to detect the probe beam characteristics at a time resolution to perform time-resolved detection of the driven resonance.

[0010] The sample may contain any material, such as any inorganic or organic material. The sample may contain gases, liquids, and / or solids. For example, the sample may contain biodetector materials, such as biological tissues or biological substances.

[0011] The sample may include nuclear magnetic resonance (NMR) and / or electron spin resonance (ESR), with its band gap matched to the radio frequency of electromagnetic radiation and / or electromagnetic evanescent field (or near field). Thus, when the sample is exposed to a radio frequency pulse containing the corresponding radio frequency, the spin resonance (i.e., electron spin resonance and / or NMR) is driven (e.g., excited), which is well known in the field of spin resonance spectroscopy, such as nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR), and electron spin resonance (ESR). The basic principles of NMR can be found, for example, in the following literature: Gutowsky, HS “Nuclear magnetic resonance.” Annual Review of Physical Chemistry 5, 1 (1954): 333-356. The basic principles of electron spin resonance (ESR) can be found, for example, in the following literature: Freed, Jack H. "New technologies in electron spinresonance.” Annual review of physical chemistry 51, 1 (2000): 655-689.

[0012] The sample is exposed to a radio frequency (RF) pump pulse that drives the sample's resonance, i.e., drives (or manipulates) the sample's (electron spin and / or nuclear magnetic resonance) resonant state. The RF pump pulse may contain an evanescent field (also known as a near field). The RF pump pulse may contain electromagnetic radiation, for example, a beam of light containing a wavelength corresponding to radio frequency. Driving is generally understood as altering the characteristics of the resonance. Driving spin resonance can be understood as (resonantly) manipulating the sample's spin state. For example, the resonance can be excited or de-excited. The RF pump pulse is the pump pulse in a pump-probe scheme used to achieve time-resolved measurements. The frequency range of RF pump pulses can be from a few Hz to hundreds of GHz. The pulse length of RF pump pulses can be from up to 60 seconds to a few nanoseconds.

[0013] The sample is placed in a magnetic bias field. The electron microscope includes a magnetic bias field generator to generate a magnetic bias field to bias the sample. The magnetic bias field generator may include a magnet, such as an electromagnet. The magnetic bias field is used to separate the states of nuclear spin resonance and / or electron spin resonance. The magnetic bias field generator can be configured to generate a vertical and / or horizontal magnetic bias field (i.e., a magnetic bias field component) relative to the main axis of the electron probe beam. During the measurement, the magnetic bias field can be constant; that is, at least during pump-probe measurements, the strength and / or orientation of the magnetic bias field relative to the main axis of the electron probe beam can be constant. For example, the field strength of the magnetic bias field can be up to 4 Tesla. The magnetic bias field can be adjustable and / or tunable; that is, the field strength and / or orientation of the magnetic bias field can be adjustable and / or tunable between consecutive measurements. The sample may contain nuclear spin resonance and / or electron spin resonance, and there is a band gap between the two spin states. For example, it is known from the Zeeman effect that the band gap between these two spin states in ESR / NMR can be manipulated by a magnetic bias field. The magnetic bias field can have a non-zero field strength, thus causing Zeeman splitting.

[0014] To detect (driven) resonances, an electron probe beam from an electron source is used. The electron source can be an electron emitter capable of producing a narrow, collimated electron beam containing electrons with kinetic energy. Suitable electron sources are well-known in the field of electron microscopy, particularly in transmission electron microscopy. Optionally, the interaction between the electron probe beam and the sample can be in a stroboscopic observation state, such that the time it takes for electrons to pass through the region of interaction with the sample's magnetic moment is significantly shorter than the timescale of the free dynamics of the spin system. The interaction between the electron probe beam and the sample can be continuous (i.e., the electron probe beam can be continuous), where the temporal resolution is provided by the detector unit.

[0015] The probe beam interacts with the sample, where the resonant state has previously been altered by a radio frequency (RF) pump pulse (i.e., by driving the resonance). For example, an RF pump pulse can excite a resonance. The interaction between the RF pump pulse and the resonance alters the magnetic moment of the sample. The probe beam may pass through the sample, or it may pass beside the sample without passing through it. However, the interaction between the probe beam and the magnetic moment of the sample causes the probe beam characteristics to be influenced by the resonant state.

[0016] The characteristics of an electron probe beam can be either the direction of the electron probe beam or the phase of the electrons within it. For example, the electron probe beam can interact with the electromagnetic potential of the sample, as described by the Aharonov-Bohm effect.

[0017] A detector unit is used to detect the probe beam characteristics of an electron probe beam. The detector unit may include, for example, a CCD camera, a CMOS camera, a pixel array detector, or an active pixel sensor. The probe beam characteristics depend on the magnetic moment of the sample, which in turn depends on the driven resonance. Therefore, the probe beam characteristics depend on the driven resonance. In other words, the probe beam characteristics indicate the interaction between the electron probe beam and the driven resonance of the sample. The driven resonance affects the probe beam characteristics. In particular, the probe beam characteristics can be proportional to the magnetic moment of the sample due to the driven resonance. Typically, the probe beam characteristics are proportional to the magnetic moment of the sample; therefore, a change in the sample's magnetic moment (due to the driven resonance) will cause a change in the probe beam characteristics. The driven resonance alters the magnetic moment of the sample interacting with electrons in the electron probe beam, thus causing the electron probe beam characteristics to change compared to before the sample is exposed to the RF pump pulse (i.e., before the driven resonance).

[0018] If the RF pump pulse does not cause any change in the sample's resonant state (such as excitation), exposing the sample to the RF pump pulse will not affect the probe beam characteristics. Therefore, in this case, the probe beam characteristics will not change.

[0019] The detector unit is configured to detect the probe beam characteristics of the electron probe beam with time resolution for time-resolved detection of the driven resonance. The time resolution of the detector unit can range from picoseconds (ps) to seconds (s). For example, the time resolution of the detector unit can range from 0.1 ps to 10 s. While the RF pump pulse used to drive the resonance includes a finite pulse length, the electron probe beam can be continuous. The time resolution of the entire method is (at least) affected by the time resolution of the detector unit and the known time relationship between the RF pump pulse and the detector unit signal. As an alternative to a continuous electron probe beam, the electron probe beam may include at least one electron probe pulse with a finite pulse length. The RF pump pulse and the electron probe pulse may include a predefined time relationship.

[0020] To account for any potential influences from the sample's surrounding environment, probe beam characteristics can be continuously measured before the sample is exposed to the RF pump pulse. This allows for continuous monitoring of probe beam characteristics as the sample is driven (e.g., excited) and the resonant state relaxes again (e.g., relaxes). The changes in probe beam characteristics caused by the interaction of the RF pump pulse with the sample are relevant for determining the resonance and, optionally, the temporal characteristics of the resonance.

[0021] The method includes the following steps: - Based on the detected characteristics of the probe beam, determine the characteristics of the resonance, especially the state of the resonance, preferably the changes in the state of the resonance.

[0022] Changes in the magnetic resonance state are caused by a radio frequency (RF) pump pulse, which (if resonant) drives the resonance. The resonant state (such as a spin state) can relax after interacting with the RF pump pulse. For example, an RF pump pulse can excite a resonant state, which then decays (after excitation). The probe beam characteristics are affected by the temporal characteristics of the (driven) resonance.

[0023] Optionally, the electron microscope includes a processing unit configured to determine the characteristics of the resonance, particularly the state of the resonance, preferably a change in the state of the resonance, based on the detected characteristics of the probe beam.

[0024] The method of this invention can use electron microscopes, particularly holographic transmission electron microscopes or ptychography transmission electron microscopes, to achieve time-resolved pump-probe resonance spectroscopy. The term "holographic transmission electron microscope" refers to a transmission electron microscope configured for electron holography or similar techniques. The term "ptychography transmission electron microscope" refers to a transmission electron microscope configured for ptychography imaging.

[0025] The electron microscope can be a transmission electron microscope (TEM). This electron microscope includes a sample holder for supporting the sample. The sample holder can be a standard TEM sample holder (also known as a TEM specimen holder). Furthermore, the electron microscope includes a radio frequency (RF) pump pulse generator for generating RF pump pulses to drive (specifically excite) the resonances of the sample, particularly electron spin resonances and / or nuclear magnetic resonances. The RF pump pulse generator may include an RF source.

[0026] In addition, an electron microscope includes an electron source for irradiating the sample with an electron probe beam. Furthermore, an electron microscope includes a detector unit for detecting probe beam characteristics, particularly the phase shift and / or deflection of the electron probe beam.

[0027] The electron microscope may also include a vacuum system having a vacuum chamber and at least one vacuum pump for evacuating the vacuum chamber. A sample holder (and a sample) may be located within the vacuum chamber. The electron microscope may include electron optics, such as at least one electron lens and / or apertures for shaping the electron probe beam and / or reference electron beam.

[0028] Typically, spin resonance spectroscopy is used to estimate / measure the local frequencies of spin resonances in a sample containing a polarized target spin set by resonantly driving (e.g., exciting) spin resonances using (tunable) radio frequency pulses. The resonance frequencies can be controlled by an external magnetic bias field, but their precise values ​​depend on the immediate environment of the spins—therefore, they can be inferred by measuring the resonance frequencies of the sample's spin resonances after the radio frequency pump pulse (e.g., using the method according to the invention). Unlike techniques known in the prior art, according to the invention, the (spin) resonances are detected (i.e., read out) by an electron probe beam. Readout by an electron probe beam provides higher spatial resolution compared to existing (spin) resonance spectroscopy techniques. In summary, this invention provides a method and electron microscope for time-resolved pump-probe resonance spectroscopy, bridging NMR / ESR and TEM, and ideally providing the spectral resolution of a spin resonance spectrometer, the spatial resolution of a transmission electron microscope, and time-resolved information on excited resonances, such as electron spin resonances and / or nuclear magnetic resonances. By utilizing and sensing the characteristics of the probe beam, particularly changes in these characteristics, for example by utilizing the Aharonov-Bohm / magnetic phase shift induced by the spin system, this invention enables the detection of real-time quantum systems using electron interferometry. These systems are influenced not only by the chemical shifts of the nearby molecular environment but also by the dynamics of the surrounding quantum states. Damage caused by irradiation can be suppressed because electrons may pass by the region of interest (i.e., electrons may not be incident on the sample). Furthermore, for certain optimized geometries, the electron wavefunction interacts only with the magnetic vector potential of the quantum system without energy transfer. Therefore, the present invention is able to detect properties that have been unavailable to free electrons, which are used as probe particles until now, thus making it possible to image quantum properties at nanometer resolution, which far exceeds the diffraction limit of radio frequency irradiation used to drive quantum systems.

[0029] Optionally, the probe beam characteristics may include the deflection of the electron probe beam. This deflection may be proportional to the magnetic moment generated by the sample due to (driven) resonance, particularly (driven) electron spin resonance and / or (driven) nuclear magnetic resonance. This deflection may be related to the change in the direction of the electron probe beam caused by the sample's magnetic moment. This deflection is caused by the Lorentz force. For example, the detector unit may include a camera for detecting the deflection. The detection of the deflection is particularly simple, thus leading to simple and robust measurements.

[0030] Optionally, the probe beam characteristics may include a phase shift in the electron probe beam. This phase shift is proportional to the magnetic moment generated by the sample due to driven (electron spin and / or nuclear magnetic) resonance. The phase is particularly sensitive to changes in the magnetic moment. Therefore, minute changes in the magnetic moment can be detected by detecting the phase shift.

[0031] For example, the method according to the invention may include the following additional step: - Provide a reference electron beam from an electron source; In this process, the reference electron beam and the electron probe beam interfere at the detector unit to form an interference beam, and the phase shift is detected by detecting the intensity of the interference beam.

[0032] For example, the electron probe beam and the reference electron beam may pass through the sample at distances d and -d, respectively (i.e., the sample is located between the electron probe beam and the reference electron beam). In this case, due to the excited spin resonance, the sample magnetic moment µ is related to the phase difference (between the electron probe beam and the reference electron beam). The relationship between them can be approximated as: = 2θ. Where:

[0033] Where e is the elementary charge, The permeability of free space, This is to reduce Planck's constant. (For a more detailed derivation, please see below.) Figure 2 (Description) For example, an electron source can be configured to provide an electron reference beam, wherein the electron probe beam and the electron reference beam interfere at least at the detector unit, forming an interference beam, and phase shift detection is achieved by detecting the intensity of the interference beam. The interference beam comprises the interference of the electron probe beam and the reference electron beam. The interference beam may be a portion of the electron probe beam that overlaps with a portion of the reference electron beam. The interference of the electron probe beam and the reference electron beam (i.e., the interference beam) is affected by the phase difference between the reference electron beam and the electron probe beam. The reference electron beam may be unaffected by any excitation of the sample, or may be affected in a manner different from that of the electron probe beam. Therefore, the (relative) phase shift of the electron probe beam and / or the reference electron beam relative to each other affects the interference beam, particularly its intensity. Thus, the intensity of the interference beam indicates a change in the sample resonance. The electron probe beam and the reference electron beam initially have a fixed phase relationship relative to each other. This phase relationship can be altered by the interaction of the electron probe beam and / or the reference electron beam with the driven spin resonance (i.e., magnetic moment) of the sample.

[0034] Electron microscopes may include electron beam splitters, particularly electron biprisms, located between the sample holder and the detector unit, such that the electron probe beam and the electron reference beam interfere at least at the detector unit.

[0035] Optionally, the interferometric beam contains a holographic signal. The reference electron beam and the electron detector beam each contain a cross section perpendicular to their respective propagation directions. The reference electron beam and the electron detector beam may overlap, such that the interferometric beam contains a cross section with a predetermined (two-dimensional) region captured by the detector unit. Within this region, the (local) intensity of the interferometric beam may vary because the phase shift of the electron detector beam may differ across its cross section. The detector unit can spatially resolve the intensity of the interferometric beam, thereby locally resolving the phase shift of the electron detector beam relative to the reference beam. The interferometric beam contains an intensity pattern at the detector unit that depends on the local phase shift of the electron detector beam relative to the reference electron beam across its cross section. The basic principles of electron holography can be found, for example, in the following literature: Lichte, Hannes, and Michael Lehmann. "Electron holography—basics and applications." Reports on Progress in Physics 71, 1 (2007): 016102.

[0036] Optionally, the resonance is a spin resonance and / or nuclear magnetic resonance, particularly a nuclear quadrupole resonance or an electron spin resonance.

[0037] For example, an RF pump pulse generator includes an antenna, particularly a coil, with the antenna adjacent to the sample. The antenna may be connected to a sample holder, for example. This arrangement of the antenna provides efficient and controllable actuation of the sample. Alternatively or supplementarily, the RF pump pulse generator may include a cavity configured to enhance the electromagnetic field of the RF pump pulse.

[0038] As examples, the invention will be further described below with reference to selected embodiments 1 to 12 (which are also shown in the accompanying drawings). However, these embodiments should not be considered as limiting the scope of this disclosure.

[0039] Example 1: A method for time-resolved pump-probe resonance spectroscopy, comprising the following steps: - Expose the sample to radio frequency pump pulses, where the radio frequency pump pulses drive the resonance of the sample, especially spin resonance and / or magnetic resonance; - The sample is probed using an electron probe beam from an electron source; - The detector unit is configured to detect the probe beam characteristics of the electron probe beam with time resolution, wherein the probe beam characteristics depend on the magnetic moment of the sample, and the magnetic moment depends on the driven resonance, for time-resolved detection of the driven resonance.

[0040] Example 2: The method according to Example 1, wherein the characteristics of the probe beam include the deflection of the electronic probe beam.

[0041] Example 3: The method according to Example 1 or Example 2, wherein the probe beam characteristics include the phase shift of the electron probe beam.

[0042] Example 4: The method according to Example 3, characterized by another step: - Provide a reference electron beam from an electron source; In this process, the reference electron beam and the electron probe beam interfere at least at the detector unit to form an interference beam, and the phase shift is detected by detecting the intensity of the interference beam.

[0043] Example 5: The method described in Example 4, wherein the interference beam contains a holographic signal.

[0044] Example 6: The method according to any of the foregoing embodiments, wherein the sample is in a magnetic bias field.

[0045] Example 7: The method according to any of the foregoing embodiments, wherein the resonance is a spin resonance and / or nuclear magnetic resonance, particularly a nuclear quadrupole resonance or an electron spin resonance.

[0046] Example 8: An electron microscope for time-resolved pump-probe resonance spectroscopy, particularly a holographic transmission electron microscope or a stacked imaging transmission electron microscope, comprising: - Sample holder, configured to support the sample; - Radio frequency pump pulse generator, used to generate radio frequency pump pulses to drive the resonance of the sample, especially spin resonance and / or magnetic resonance; - An electron source used to irradiate the sample with an electron probe beam; - A detector unit for detecting probe beam characteristics of an electron probe beam, particularly phase shift and / or deflection, wherein the probe beam characteristics depend on the magnetic moment of the sample, wherein the magnetic moment depends on the driven resonance, the detector unit being configured to detect the probe beam characteristics at a time resolution for time-resolved detection of the driven resonance.

[0047] Example 9: An electron microscope according to Example 8, characterized in that the probe beam characteristics include a phase shift of the electron probe beam, wherein the electron source is configured to provide an electron reference beam, wherein the electron probe beam and the electron reference beam interfere at least at the detector unit and form an interference beam, wherein the phase shift is detected by detecting the intensity of the interference beam.

[0048] Example 10: An electron microscope according to Example 8 or Example 9, characterized in that an electron beam splitter, particularly an electron biprism, is placed between the sample holder and the detector unit, such that the electron probe beam and the electron reference beam interfere at the detector unit.

[0049] Example 11: An electron microscope according to any one of Examples 8 to 11, characterized in that it is provided with a magnetic bias field generator for generating a magnetic bias field to bias the sample.

[0050] Example 12: An electron microscope according to any one of Examples 8 to 11, characterized in that the radio frequency pump pulse generator includes an antenna, particularly a coil, wherein the antenna is adjacent to the sample. Attached Figure Description

[0051] As examples, the present disclosure will be further described with reference to some selected embodiments shown in the accompanying drawings. However, these embodiments should not be considered as limiting the present disclosure.

[0052] Figure 1 An electron microscope schematically illustrates a pump-probe resonance spectrum for time-resolved imaging. Figure 2 A simplified model of the interaction between electrons and magnetic moments in a Mach-Zehnder interferometer apparatus is schematically shown.

[0053] Figure 3A and 3B Two exemplary spectral protocols are shown. Detailed Implementation

[0054] Figure 1 An electron microscope 1 for time-resolved pump-probe resonance spectroscopy is schematically illustrated. In this exemplary embodiment, the electron microscope 1 is configured as a holographic transmission electron microscope. The electron microscope 1 includes a sample holder 3 for supporting a sample 4. Furthermore, the electron microscope 1 includes a radio frequency pump pulse generator 5 for generating radio frequency pump pulses 20 (e.g., see Figures 4A and 4B) to drive a resonance in the sample 4, which in this exemplary embodiment is a spin resonance. A bias magnetic field 22 is present within the electron microscope 1 for energy-wise separation of the spin states of the sample 1. An electron source 6 is provided for irradiating the sample 4 with an electron probe beam 7. A detector unit 8 is provided for detecting the probe beam characteristics of the electron probe beam 7, in this example, the phase shift of the electron probe beam 7, wherein the probe beam characteristics depend on the magnetic moment 25 of the sample 4, particularly on the change in the magnetic moment 25 caused by the driven spin resonance. The detector unit 8 is configured to detect the probe beam characteristics in a time-resolved manner, thereby performing time-resolved detection of the driven spin resonance. For example, the time resolution is set for time-resolved detection of the excitation of the sample 4. The probe beam characteristics include the phase shift of the electron probe beam 7, where the phase shift depends on the magnetic moment 25 of the sample 4 (see...). Figure 2 Specifically, the phase shift depends on the change in magnetic moment 25 caused by the driven resonance. The electron source 6 is configured to provide an electron reference beam 9. In this exemplary embodiment, the electron probe beam 7 propagates through the sample 4, while the reference electron beam 9 passes beside the sample 4 such that the reference electron beam does not incident on the sample 4 and therefore does not propagate through it. The electron probe beam 7 and the electron reference beam 9 interfere at least at the detector unit 8, forming an interference beam 10, wherein the phase shift is detected by detecting the intensity of the interference beam 10. To achieve the interference between the electron probe beam 7 and the reference electron beam 9, in this exemplary embodiment, an electron beam splitter (in this exemplary embodiment, an electron biprism 11) is placed between the sample holder 3 and the detector unit 8 such that the electron probe beam 7 and the electron reference beam 9 interfere (at least) at the detector unit 8. The electron biprism includes two groundable electrodes 11a and a filament electrode 11b. A magnetic bias field generator (not shown) generates a magnetic bias field 22 (B0) to bias the sample 4.

[0055] The radio frequency pump pulse generator 5 may include an antenna, such as a coil. This radio frequency pump pulse generator is adjacent to the sample.

[0056] In addition, the electron microscope 1 also includes an electron lens 15 for shaping the electron probe beam 7 and the reference electron beam 9.

[0057] Optionally, sample 1 may be subjected to additional cooling or hyperpolarization treatment, which causes more significant spin polarization, thereby further increasing the interference phase shift or deflection of electrons.

[0058] The method for time-resolved pump-probe resonance spectroscopy includes the following steps: - Expose sample 4 to RF pump pulse 20 (see Figure 3A and 3B ), in which the radio frequency pump pulse 20 drives the resonance of sample 4, especially spin resonance and / or magnetic resonance; - Sample 4 is detected using an electron detection beam 7 from electron source 6; - The detection beam characteristics of the electron probe beam 7 are detected using detector unit 8. These characteristics depend on the magnetic moment 25 of the sample 4, and particularly on the change in magnetic moment caused by driven resonance. Detector unit 8 is configured to detect the detection beam characteristics of the electron probe beam 7 with time resolution, thereby enabling time-resolved detection of driven resonance; and - Based on the detected characteristics of the probe beam, determine the characteristics of the resonance, especially the resonance state, preferably the changes in the resonance state.

[0059] The probe beam characteristics include the phase shift of the electron probe beam 7. The phase shift depends on the magnetic moment 25 of sample 4. Magnetic moment 25 depends on the driven resonance, i.e., in this case, on the state of the spin resonance. For the relationship between phase shift and magnetic moment 25, please refer to [link to relevant documentation]. Figure 2 and about Figure 2 The discussion.

[0060] In addition, a reference electron beam 9 from electron source 6 is provided. The reference electron beam 9 and the electron probe beam 7 interfere at detector unit 8 to form an interference beam, wherein phase shift is detected by detecting the intensity of the interference beam 10. In this exemplary embodiment, the interference beam 10 contains a holographic signal, as shown by fringe 21 on detector unit 8. Sample 4 is placed in a magnetic bias field 22 generated by a magnetic bias field generator (not shown). In this example, the spin resonance is nuclear magnetic resonance.

[0061] Figure 2 A simplified model of the interaction between electron 16 and the magnetic moment µ(t) 25 of sample 4 in a Mach-Zehnder device 17 is schematically illustrated. The Mach-Zehnder device 17 includes two electron beam splitters 18 and two electron paths 23, 24 (also called arms), denoted by |L> and |R>, respectively. Sample 4 ( Figure 2 Not shown in the image, see [link / reference]. Figure 1The electron beams in these two electron paths 23 and 24 are located between the electron detector beam 7 and the reference electron beam 9, respectively.

[0062] A sparse beam of electrons 16 propagating at velocity v in the z-direction (see coordinate system 19) (such as electron probe beam 7 or reference electron beam 9) is coherently split into two distinct arms (i.e., paths 23 and 24) spaced Δy = 2d apart, each arm passing through sample 4. Sample 4 is characterized by a spatially fixed and well-localized magnetic moment. (t)25 describes a magnetic moment with a given time-varying orientation, located precisely between the two arms in the yz plane. The electron beams in the two arms are separated at a greater distance from sample 4 compared to the shortest distance electron 16 travels through sample 4.

[0063] Sample 4 will interact with the moving electron 16, thereby establishing a relative phase (i.e., phase shift) between the interferometer arms (i.e., electron paths 23, 24). This will change the probability (due to the phase shift) that electron 16 can be detected at one of the two output ports 26, 27 (denoted by <+| and <-|) when the two electron paths 23, 24 recombine. This is the measurement signal, through which the magnetic moment of sample 4 can be monitored when sample 4 is driven by the RF pump pulse 20. (t) 25 changes.

[0064] Each electron is a moving charge that generates a magnetic field and magnetic moment at the sample location (y, z = 0). (t)25 interaction. Given the transit time The two Mach-Zehnder arm states |L> and |R> correspond to electron 16 along the trajectory z = v(t- )exist = -d and = Point d passes through sample 4. The corresponding magnetic field of electron 16 is:

[0065] For |L>, and -B(t) for |R> (see JD Jackson, Classical alelectrodynamics (Wiley, New York, 1999)).

[0066] here, Let e ​​represent the vacuum permeability, e represent the electron charge, and v represent the electron velocity. This represents the Lorentz factor.

[0067] The resulting interaction Hamiltonian function can be written as: , In this example, the slight deflection of the electron trajectory caused by this potential is ignored. For a quantitative estimate of this correction, please refer to Example B below.

[0068] Unlike the macroscopic magnetic moment 25 in sample 4, which is largely unaffected by the passage of the probe electron, the focus here is on a single spin-1 / 2 quantum region, which is relative to the bias field 22. = Alignment is achieved, and the input state |ψ> is prepared by a short RF pump pulse 20. For this purpose, µ(t) is replaced with a freely manipulated spin operator: ; (1) use Let µ denote the Pauli matrix vector, and let µ denote the appropriate magnetic moment (e.g., for electron spin, µ = ...). ,in It is the gyromagnetic ratio of electrons. It is the Bohr magneton of the electron. It is the mass of electrons. This represents the relevant Larmor frequency. This frequency describes the precession of the spin about the magnetic field axis n. Example C gives an extension to the case of collective spin.

[0069] Since it is assumed to operate in strobe mode, electron 16 communicates with... The interaction region of (t) 25 has a time scale much shorter than the time scale of the free dynamics of the spin system. If the state of the spin system is n If the two eigenstates are incoherently mixed, then the timescale is defined by the decay of spin polarization.

[0070] If the state of a spin system is a (partial) coherent superposition of two eigenstates, then the timescale of the spin dynamics is defined by the reciprocal of the Larmor frequency. Therefore, the magnetic moment µ(t)²⁵ can be approximated as µ(t) ≈ µ(t)²⁵ over the duration of a single electron pulse. Furthermore, it was found that the interaction Hamiltonian function Hint(t) gives a unitary transform representing the passage of electrons.

[0071] The unitary normal transform describes the path-dependent phase shift of electrons controlled by the sample spin. Therefore, the interferometry will read out the x-projection of the sample magnetic moment 25 via a relative phase 2θ. The unitary normal transform also describes the measurement reaction exerted by the electrons: a controlled spin rotation of the sample ±θ angle. This can cause entanglement between the sample 4 and the electron states, leading to a loss of interferometric visibility. It is assumed that the electrons split into a superposition state.

[0072] With φ being an adjustable external phase shift, the combined sample-electronic states become

[0073] Given that |φ + π> and |φ> are orthogonal, unless |ψ> is x The eigenstate of (t0) is either an entangled state or a combination state. To complete the measurement, the two arms of the interferometer are merged at the beam splitter. Finally, electron 16 is detected at one of the two output ports 26 and 27, for example, |+> = (|R> + |L>) / √2 and |-> = (|R> - |L>) / √2, i.e., |+>.

[0074] The probability of this happening, (2) It carries information about the sample's average spin x-component at the time of detection, i.e., < ( )> = <ψ| ( The expected value here is denoted by <.> relative to the sample state, and note that the result can be extended to classical mixtures of pure states. The sample pair is composed of... The effect of the described interference signal is twofold: first, it shifts the sinusoidal fringes by the net phase.

[0075] Secondly, it reduces the contrast or visibility of the stripes in the following ways.

[0076] At a visibility of ν=100%, < > = ±1, Δ = ±2θ. This is similar to ideal, reaction-free sensing of a fixed magnetic moment 25 by sensing a relative phase shift of 2θ (see Example A).

[0077] In general, the x-component of the spin vector < >It will be at the precession frequency of Lamor As The function oscillates (unless the bias field 22 is along n = (Direction). Therefore, by... The sample is periodically probed at a fixed modulus of 2π, and different external phases are recorded. The number of electrons under the current can be used to obtain a predicted phase shift Δ. Interference fringes with visibility.

[0078] The following paragraphs will discuss achievable measurement accuracy and elucidate the interaction between phase shift and visibility reduction in interferometric readout.

[0079] If we assume that the current is measured at the two output ports 26 and 27 respectively, the interaction strength θ can be inferred from the average current difference. This average current difference is related to 2 (θ, ; The measurement uncertainty is proportional to -1. The variance of the current difference is given by the limiting case of repeated measurements, which is correspondingly converted into the mean square error Var[θ].

[0080] According to Gaussian error propagation law, we can conclude that in an interferometer, for Ne non-interacting electrons, the maximum accuracy achievable through intensity measurements at two ports is √(Var[θ]) = 1 / 2√Ne. This is true regardless of whether phase or visibility is used as the observable. However, the situation changes when considering multiple spin systems in coherent states at the same location. In this case, when the phase is at its maximum, the maximum phase is proportional to the spin number Ns, and the maximum accuracy is proportional to 1 / Ns; while when the phase disappears and visibility decreases to its maximum, the maximum accuracy is proportional to 1 / √Ns. See Example C for the derivation and detailed discussion.

[0081] Next, we will discuss two exemplary spectral schemes for spin samples, such as Figure 3A and Figure 3B As shown. Axis 28 schematically represents the process or time sequence. From left to right, the magnetic moment µ 25 starts from an initial state, where the radio frequency pump pulse 20 subsequently drives resonance, in this exemplary embodiment, spin resonance, (causing a change in the magnetic moment µ 25) to another state. On the right side of the figure, the states read by the interferometer device 17 are shown. Figure 3A and Figure 3B Coordinate system 29 is shown.

[0082] exist Figure 3B In the middle, the bias field 22 (see Figure 1 ) points to The direction enables the interferometer (i.e., interferometer device 17) to detect time-independent spin polarization. x( )> = < x>= This will result in an average phase shift of arctan( tan2θ), if the spin state is a mixed state (| If | < 1), visibility will decrease. If a resonant RF pulse of length π (i.e., RF pump pulse 20) is now applied, the magnetic moment will be flipped, allowing for differential phase measurements. Coupling with the environment (especially the electromagnetic vacuum) will cause the state to change over the lifetime. Internal attenuation.

[0083] exist Figure 3A In this context, a strong bias field 22 is considered, which sets the spin quantization axis to n = , making ( ) = cos( ) + y sin( Initial and Aligned or antialigned spin states, or a mixture of these states (where < > = ∈ [-1, 1] and < >= 0) will result in a decrease in visibility of |cos 2θ|, but no net phase shift. If subsequently applied with A suitable RF pulse of resonant length π / 2 (i.e., RF pump pulse 20) will cause the spin to < ( )> = sin The rate precession of this precession results in an oscillatory phase shift and increased visibility. In the pure spin state ( In the optimal case (±1), the phase shifts periodically by up to ±2θ under full visibility. When For π / These maximum absolute phase shifts can be obtained when the precession spin vector is an integer multiple of the interferometer plane, i.e., when the precession spin vector is orthogonal to the interferometer plane. To detect this precession, one can utilize... Time resolution on the order of 10.

[0084] Along the x-axis (< Interferometer phase shift difference between two spin directions > = ±1),

[0085] This depends on the strength of the magnetic dipole moment, where This refers to the gyromagnetic ratio (e.g., the gyromagnetic ratio of an electron spin is approximately 2π*28 GHz / T, with a lifetime on the order of 100 nanoseconds; the gyromagnetic ratio of a nuclear hydrogen spin is approximately 2π*42.6 MHz / T, with a lifetime on the order of seconds). Probing a single electron spin at a distance of 1 nanometer via interferometry results in approximately 2.2 × 10⁻⁶ GHz / T. A phase shift difference of mrad. Therefore, single electron spin detection under quantum projection noise confinement requires only <5× One electron (a typical beam current in a TEM is 1.5 nA, equivalent to approximately (electrons / second).

[0086] Unlike the basic case of a single spin, a more realistic situation is the study of... A coherent set of spins. In this case, the maximum phase obtained is 2. θ. Details of the derivation of this result can be found in Example C. In transmission electron microscopy, samples with a thickness of approximately 100–200 nm are typically examined, allowing atomic columns of about 1000 atoms to interact / contribute. Real samples are not perfectly coherent and are point-like. In particular, finite-temperature effects only result in partial polarization of the spin sample, while finite size leads to additional geometric factors, as illustrated by the example of the classically magnetized sphere in Example D. Under high-temperature conditions, It can be estimated that only a small portion spin number The net magnetization of the sample constituting the electron detector. In this geometry, even the weak phase shift caused by nuclear hydrogen spin accumulates and becomes detectable, especially because nuclear spins have very long coherence times, on the order of seconds. A brief derivation of the phase shift caused by a sample with I = 1 / 2 nuclear spin, based on the classical magnetization model, can be found in Example E.

[0087] To experimentally explore spin dynamics, a strong magnetic field (which can be generated by two magnetic pole pieces) is used to polarize the sample's spin. This method requires an ultrafast transmission electron microscope (UTEM) precisely synchronized with the precession frequency. Figure 3A .

[0088] Another option is to place the spin sample in a magnetic field perpendicular to the interferometer axis (using the so-called Lorentz mode and an additional magnetic bias field, an in-plane magnetic field, see...). Figure 3B This geometry allows for the use of π / 2 pulses to eliminate any magnetic flux passing through the interferometer region due to spin-vertical precession, or the use of π pulses to reverse the magnetic flux and maximize the phase shift, thus relaxing the time resolution required for these pump-probe configurations to the lifetime of the spin state. Recent advances in electronic detection techniques (Timepix3, Timepix4) have enabled the time resolution of these projection dynamics to reach nanosecond-level accuracy.

[0089] Example A: Phase shift induced by a point-like classical magnetic dipole In this example, we start from the effect of the classical magnetic dipole's magnetic field on the electron wave function, rather than considering the effect of the electron's magnetic field on the dipole. Under the assumption that the vector potential generated by the magnetic dipole during the interaction can be approximated as constant, the dipole is assumed to be oriented along the x-direction, therefore:

[0090] Assuming the de Broglie wavelength of the electron is much smaller than the characteristic scale of the electromagnetic field, the eikonal approximation can be used, where the phase is given by the action along the classical trajectory. In this case, and assuming non-relativistic propagation, the relative phase between the propagation of the quantum system and the quantumless system is...

[0091] Where Δv(t) is the velocity change caused by the electromagnetic field, and r(t) is the trajectory of the electron under the influence of the electromagnetic field. These can be derived from the Lorentz force law.

[0092] As a formal solution

[0093] Wherein, the initial trajectory and the initial velocity are respectively and = (0, 0, ), in which Cartesian coordinates x = (x, y, z) were chosen. This means and

[0094] In the first order of e|A| / mc, for θ = π / 2

[0095] Restore the main text regarding the phase difference Δ between the two interferometer arms. = 2θ result.

[0096] Example B: Electron deflection Spin transitions in spin systems induced by electron pulses are described in (D. Rätzel, D. Hartley, O. Schwartz, and P. Haslinger, “Controlling Quantum Systems with Modulated Electron Beams”, Phys. Rev. Research 3, 023247(2021)). In the event of such a transition, if the following conditions are met... and If the reaction force on the electron is negligible, then Δz and Δr⊥ represent the longitudinal and transverse widths of the electron wave packet, respectively, and d is the collision parameter (the minimum distance between the electron and the spin system during the interaction). The first condition essentially means that, in the case of a spin system transition, the momentum transfer to the electron corresponding to the kinetic energy exchanged with the spin system must be much smaller than the longitudinal momentum broadening of the electron. Even without a transition, the interaction between the electron and the spin system may still cause the electron to deflect laterally along its initial propagation direction. To approximate this small change in transverse velocity, a classical magnetic dipole moment is chosen as the source of the magnetic field, and the orientation of this magnetic field is set to maximize the Lorentz force acting on the electron.

[0097] Then, it was discovered

[0098] Assumption Given that the distance d = 0.1 nm, Δv is obtained. 60 m / s.

[0099] Example C: Multiple spins Next, assuming The spin system is located at the same position in the middle of the interferometer plane. Compared to the above description, the time evolution operator is replaced with...

[0100] in, Acting on the tensor product space of the Hilbert spaces of each spin system, and for i ≠ m, we have ( m = and( i = Each individual The time evolution is given by equation (1). |in, NS> is assumed to be a coherent spin state, where all individual spins are in the same pure state. .

[0101] Similar to the specific schemes mentioned above, we first consider <ψ| ( The case where )|ψ> disappears. Because <ψ | | ψ>=0 and <ψ | Since | ψ>=1, the following result is obtained:

[0102] in:

[0103] This means the phase shift disappears, and the visibility is... V = (2θ). When When = 0, the variance becomes

[0104] For small θ, Var[θ] ≥ 1 / (4NeNs).

[0105] For the second case, assume |ψ> is If an eigenstate has an eigenvalue of 1, then:

[0106] This means that the phase shift Δ = 2Nsθ, visibility V = 1, and the accuracy limit Var[θ] ≥ 1 / (4NeNs²). It has been found that the induced phases on the electron interferometer are coherently superimposed, and the inference accuracy of the interaction strength increases with increasing Ns, while the inference accuracy of the decoherence process increases with increasing √Ns. In the limiting case where Ns is very large, the phase becomes the only relevant observable, and the results can be compared with the case of the phase induced by the classical (precessing) magnetic dipole moment in the electron interferometer.

[0107] Example D: Phase shift caused by magnetic polarization at finite temperatures The above considerations are limited to point-like spin systems compared to the extension of the electron interferometer. To understand how the situation changes when multiple spin systems are distributed over a length scale similar in size to the interferometer, the scope here is limited to the classical model of spin systems. As mentioned above, if the interaction with the electron is stroboscopic, i.e., the duration of the effective interaction is much shorter than the characteristic timescale of the magnetic moment change (such as the precession period), and if a sufficient number of spins are perpendicular to the electron interferometer plane when interacting with the electron pulse, such that the phase shift also dominates the decoherence process, then this should provide accurate results.

[0108] The spin system is then modeled as a paramagnetic sphere with a uniform, isotropic magnetic susceptibility χ, which is placed in a uniform magnetic field. The resulting uniform polarization is

[0109] Where µ = (1 + χ) And to obtain an approximate result, assume χ << 1. The magnetic field induced by magnetization inside the sphere is...

[0110] If we assume that the spin vector corresponding to this magnetization is subjected to an ideal π / 2 pulse (see... Figure 3A The resulting precession will lead to an oscillating magnetic field with an amplitude of = | | = 2χB0 / 3. If a π pulse is applied (see...) Figure 3B If the magnetization is reversed, the magnetic flux will be reversed. If the sphere is placed in the interferometer so that its cross-section within the interferometer plane is maximized, the maximum magnetic flux obtainable is Φ = π. , where R is the radius of the sphere.

[0111] In bias field 22 In the middle, the energy induced between electron spin states splits into ,in This is the gyromagnetic ratio of electrons. Next, consider a paramagnetic electron spin medium, whose temperature satisfies... In this case, it is found that for magnetic susceptibility (whose spin I = 1 / 2 and = As far as ) .

[0112]

[0113] in, = / V represents electron spin density. V is the number of electron spins in the sphere, and V is the volume of the sphere. For magnetic flux, we find the following equation:

[0114] Regarding the magnetic phase in electron MZI, the following equation is found:

[0115] Except for the Boltzmann factor and the numerical factor π / 4, all other results were restored to those in the previous section.

[0116] Example E: Nuclear Magnetic Resonance For the spin of the atomic nucleus, calculations were performed similar to those for the interaction between free electrons and electron spin. We simply consider... ,in = e / (2 ) is a nuclear magnetic particle, This is the total nuclear spin g-factor. For simplicity, we assume the nuclear spin is also 1 / 2 and is represented using the same Pauli matrices as in the previous case. Therefore, by replacing the coupling parameter θ with the following equation, all the above equations can be recovered.

[0117] in It is the nuclear gyromagnetic ratio, which depends on the atom being probed. The resulting phase shift is...

[0118] Similar to the analysis above, the calculation was also performed when... T>> At that time, the phase shift caused by classical magnetization corresponding to nuclear spin is

[0119] Phase change

[0120] For the case of I = 1 / 2, the following equation is found.

[0121] 2 Restore to the Boltzmann factor and the numerical factor π / 4.

Claims

1. A method for time-resolved pump-probe resonance spectroscopy, comprising the steps of: - Expose the sample (4) to a radio frequency pump pulse (20), wherein the radio frequency pump pulse (20) drives the resonance of the sample (4), wherein the resonance is an electron spin resonance and / or nuclear magnetic resonance, wherein the sample (4) is located in a magnetic bias field (22). - The sample (4) is probed using an electron probe beam (7) from an electron source (6); - The detection beam characteristics of the electron detection beam (7) are detected using the detector unit (8), wherein, The probe beam characteristics depend on the magnetic moment (25) of the sample (4), wherein the magnetic moment (25) depends on the driven resonance, wherein the detector unit (8) is configured to detect the probe beam characteristics of the electron probe beam (7) at a time resolution to perform time-resolved detection of the driven resonance; and -Based on the detected characteristics of the probe beam, determine the characteristics of the resonance, especially the state of the resonance, preferably the change in the state of the resonance.

2. The method according to claim 1, wherein, The characteristics of the probe beam include the deflection of the electron probe beam (7).

3. The method according to claim 1 or claim 2, wherein, The characteristics of the probe beam include the phase shift of the electron probe beam (7).

4. The method according to claim 3, characterized in that... Including another step: - A reference electron beam (9) is provided from the electron source (6); The reference electron beam (9) and the electron probe beam (7) interfere at least at the detector unit (8) to form an interference beam (10), wherein the phase shift is detected by detecting the intensity of the interference beam (10).

5. The method according to claim 4, characterized in that, The interference beam (10) contains a holographic signal (21).

6. An electron microscope (1) for time-resolved pump-probe resonance spectroscopy, particularly a holographic transmission electron microscope or a stacked imaging transmission electron microscope, comprising: - Sample holder (3) for supporting sample (4); - Radio frequency pump pulse generator (5) for generating radio frequency pump pulses (20) to drive the resonance of the sample (4), wherein the resonance is an electron spin resonance and / or nuclear magnetic resonance; - A magnetic bias field generator for generating a magnetic bias field (22) to bias the sample (4); - An electron source (6) is used to irradiate the sample (4) with an electron probe beam (7); - Detector unit (8) for detecting the probe beam characteristics of the electron probe beam (7), particularly phase shift and / or deflection, wherein the probe beam characteristics depend on the magnetic moment (25) of the sample (4), wherein the magnetic moment (25) depends on the driven resonance, wherein the detector unit (8) is configured to detect the probe beam characteristics at a time resolution to perform time-resolved detection of the driven resonance.

7. The electron microscope (1) according to claim 6, characterized in that, The characteristics of the probe beam include the phase shift of the electron probe beam (7), wherein the electron source (6) is configured to provide an electron reference beam (9), the electron probe beam (7) and the electron reference beam (9) interfere at least at the detector unit (8) and form an interference beam, wherein the phase shift is detected by detecting the intensity of the interference beam (10).

8. The electron microscope (1) according to claim 6 or claim 7, characterized in that, An electron beam splitter, particularly an electron biprism (11), is provided between the sample holder (3) and the detector unit (8) so that the electron probe beam (7) and the electron reference beam (9) interfere at the detector unit (8).

9. The electron microscope (1) according to any one of claims 6 to 8, characterized in that, The radio frequency pump pulse generator (5) includes an antenna, particularly a coil, wherein the antenna is adjacent to the sample (4).

Images