A high-resolution coaxial velocity imaging device

Abstract

The present invention provides a high-resolution coaxial velocity imaging device, which relates to the field of energy spectrum analysis equipment. The high-resolution coaxial velocity imaging device provided by the present invention includes an analysis chamber, a gas injection mechanism, a vacuum mechanism, an electrostatic lens and an image acquisition mechanism; one end of the analysis chamber is provided with a light inlet window suitable for allowing laser light to pass through, and the image acquisition mechanism passes through one end of the analysis chamber and is connected to the inner cavity of the analysis chamber; the gas injection mechanism and the vacuum mechanism are both provided on the side wall of the analysis chamber and are both connected to the inner cavity of the analysis chamber, and the electrostatic lens is provided in the inner cavity of the analysis chamber. The optical path of the laser, the electrostatic lens and the image acquisition mechanism in the present invention are located on the same axis, which is usually the central axis of the analysis chamber, and a reflector is also provided in the electrode sheet to reflect the laser light, so that the momentum distribution image of electrons or ions on the polarization plane can be directly obtained.

Description

Technical Field

[0001] The present invention relates to the field of energy spectrum analysis equipment, in particular to a high-resolution coaxial velocity imaging device. Background Art

[0002] In the study of the interaction of intense lasers with atoms and molecules, a key goal is to obtain information such as product yield, energy distribution, angular distribution, and velocity distribution. Velocity imaging technology, capable of simultaneously measuring these interrelated quantities and revealing the dynamics of atomic and molecular reactions, has become an important tool for probing molecular microdynamics. Velocity imaging spectrometers are also popular due to their simple and easy-to-understand reaction principles, ultra-high energy resolution, and 100% × 4π full solid angle collection efficiency. They have become standard experimental tools for many atomic and molecular photophysics research groups.

[0003] However, in traditional velocity imaging spectrometer designs, the laser's polarization plane is perpendicular to the detector plane, making it impossible to conduct polarization-dependent angular distribution experiments on electrons or ions. To overcome this limitation, coaxial velocity imaging spectrometers (co-axial velocity map imaging) have emerged. In this type of velocity imaging spectrometer, the laser propagates along the spectrometer's axis, with the laser's polarization plane parallel to the detector plane. Compared to traditional velocity imaging spectrometers, coaxial velocity imaging spectrometers can easily and accurately obtain angular distribution images of electrons or ions along the polarization plane, demonstrating significant advantages in laser experiments involving multiple polarization characteristics. However, while coaxial velocity imaging spectrometers can capture momentum distribution images along the laser's polarization plane, their image acquisition mechanism cannot withstand the energy of the direct laser beam, necessitating the use of a specially customized image acquisition mechanism to make way for the laser. This image acquisition mechanism is not only expensive and complex in structure, but is also typically not adjusted after a single installation.

[0004] In summary, there is a need for a coaxial velocity imaging spectrometer that can avoid direct laser radiation. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a high-resolution coaxial velocity imaging device that can reflect laser light and directly obtain the momentum distribution image of electrons or ions on the laser polarization plane.

[0006] The present invention provides a high-resolution coaxial velocity imaging device, comprising an analysis chamber, a gas injection mechanism, a vacuum mechanism, an electrostatic lens, and an image acquisition mechanism; one end of the analysis chamber is provided with a light-inlet window suitable for allowing laser light to pass through, the image acquisition mechanism passes through one end of the analysis chamber and is connected to the inner cavity of the analysis chamber; the gas injection mechanism and the vacuum mechanism are both provided on the side wall of the analysis chamber and are both connected to the inner cavity of the analysis chamber, the electrostatic lens is provided in the inner cavity of the analysis chamber; the electrostatic lens comprises a first electrode sheet group, a second electrode sheet group, and a plurality of electrodes arranged in sequence along the axial direction of the analysis chamber. The first electrode sheet group and the third electrode sheet group, the first electrode sheet group is close to the light-inlet window; the first electrode sheet group, the second electrode sheet group and the third electrode sheet group each include a plurality of electrode sheets, each of which is provided with a through hole; the gas injection mechanism includes a gas cylinder, an air inlet pipe assembly and a hollow needle connected in sequence, and the hollow needle is located between two electrode sheets in the second electrode sheet group; a metal mesh is further provided in the through hole of the electrode sheet close to the third electrode sheet group in the second electrode sheet group, and a reflector is further provided on the metal mesh; the optical path of the laser, the reflector and the image acquisition mechanism are located on the same axis.

[0007] In a feasible embodiment of the present invention, a fixing rod is further provided in the inner cavity of the analysis chamber, and the fixing rod is sequentially passed through all the electrode sheets; a plurality of fixing nuts and a plurality of isolation washers are also provided on the fixing rod, wherein two of the fixing nuts are respectively located at the two ends of the fixing rod and all the electrode sheets are located between the two fixing nuts, and one or more isolation washers are provided between adjacent electrode sheets.

[0008] In a feasible embodiment of the present invention, the thickness of the isolation gasket is 1 to 5 mm; and / or the thickness of the electrode sheet is 1 to 136 mm; and / or the diameter of the opening in the electrode sheet is 15 to 88 mm; and / or the transmittance of the metal mesh is ≥80%, the mesh number of the metal mesh is ≥180 mesh, and the wire diameter of the metal mesh is ≤0.015 mm; and / or the thickness of the reflector is 1 to 3 mm, and the diameter of the reflector is 5 to 15 mm; and / or the materials of the fixing rod, fixing nut and isolation gasket are all ceramic.

[0009] In a feasible embodiment of the present invention, the first electrode sheet group includes N electrode sheets, and the first electrode sheet group is used to protect the uniform electric field; the second electrode sheet group includes M electrode sheets, and the second electrode sheet group is used to form a uniform electric field; the third electrode sheet group includes P electrode sheets, and the third electrode sheet group is used to form a drift electric field; wherein N, M and P satisfy the following relationship

[0010] 4≤N+M+P≤16

[0011] 1≤N≤2, 2≤M≤8, 1≤P≤6.

[0012] In a feasible embodiment of the present invention, the first electrode sheet group includes 2 electrode sheets, namely electrode sheet No. 1 and electrode sheet No. 2; the second electrode sheet group includes 8 electrode sheets, namely electrode sheet No. 3 to electrode sheet No. 11; the third electrode sheet group includes 6 electrode sheets, namely electrode sheet No. 12 to electrode sheet No. 16; a drift tube is also provided in the electrode sheet No. 16; the hollow needle is located between electrode sheet No. 5 and electrode sheet No. 6; one or more resistors are provided between each of the electrode sheets No. 3 to No. 10; metal mesh is provided in the through holes of the electrode sheet No. 11 and the electrode sheet No. 12, and a metal mesh is also provided in the through hole of the electrode sheet No. 6 near the end of the image acquisition mechanism, and the reflector is provided on the metal mesh of the electrode sheet No. 11; the electrode sheets No. 1 to No. 3 and the electrode sheets No. 11 to No. 16 are all individually connected to high-voltage connectors.

[0013] In a feasible embodiment of the present invention, the thickness of electrode sheets No. 1 to No. 3 is 1 mm, and the diameter of the through holes is 15 mm; the thickness of electrode sheets No. 8 to No. 10 is 1 mm, and the diameter of the through holes is 88 mm; the thickness of electrode sheets No. 11 to No. 15 is 4 mm, and the diameter of the through holes is 88 mm; the total thickness of electrode sheet No. 16 is 131 mm, the thickness of the drift tube is 123 mm, the thickness of electrode sheet No. 16 at both ends of the drift tube is 8 mm, the through hole diameter of electrode sheet No. 16 and the inner diameter of the drift tube are both 88 mm; the transmittance of the metal mesh is 80%, the material of the metal mesh is 316L stainless steel, the mesh number of the metal mesh is 180, and the wire diameter of the metal mesh is 0.015 mm; the diameter of the reflector is 10 mm, the thickness is 0.3 mm, the substrate of the reflector is silicon dioxide, the surface of the substrate is fully gold-plated, the front side is gold-plated with 150 nm, and the side and back sides are gold-plated with 20 nm.

[0014] In a feasible embodiment of the present invention, a magnetic shielding mechanism is further provided in the inner cavity of the analysis cavity, and the magnetic shielding mechanism includes a first magnetic shielding cavity, a second magnetic shielding cavity and a third magnetic shielding cavity arranged in sequence from the inside to the outside; the electrostatic lens is arranged in the first magnetic shielding cavity.

[0015] In a feasible embodiment of the present invention, the gas injection mechanism also includes a three-dimensional movable platform, the air intake pipe assembly includes a 1 / 4-inch tube and a 1 / 8-inch tube connected and communicated in sequence, one end of the 1 / 8-inch tube is connected and communicated with a hollow needle; the three-dimensional movable platform is arranged on the outside of the 1 / 4-inch tube and is connected to the 1 / 4-inch tube.

[0016] In a feasible embodiment of the present invention, the image acquisition mechanism includes an MCP, a fluorescent screen and a camera sequentially arranged along the axial direction of the analysis cavity, and the MCP is close to the third electrode sheet group.

[0017] The present invention also provides a method for using a high-resolution coaxial velocity imaging device, comprising at least the following steps:

[0018] 1) The laser enters the inner cavity of the analysis chamber through the light inlet window and ionizes the sample molecules injected by the gas injection device in the reaction zone, generating electrons and ions;

[0019] 2) The sample molecules are ionized to generate electrons and ions. The electrons or ions are focused on the image acquisition mechanism under the action of the electrostatic lens and are collected by the image acquisition mechanism.

[0020] The high-resolution coaxial velocity imaging device provided by the present invention has the following beneficial effects:

[0021] 1) The optical path of the laser, the electrostatic lens, and the image acquisition mechanism in the present invention are located on the same axis, which is usually the central axis of the analysis cavity, and a reflector is also provided in the electrode sheet to reflect the laser, so that the momentum distribution image of the electron or ion on the polarization plane can be directly obtained; at the same time, the structure of the present invention is not complicated and is modularized as a whole, which relatively simplifies the difficulty of installation, operation, and debugging.

[0022] 2) In a specific embodiment of the present invention, there are a total of 16 electrodes, and the voltage of each electrode is carefully designed to more accurately control the flight trajectory of electrons and ions, with a resolution of up to 1% @ 60eV.

[0023] 3) The present invention provides a first magnetic shielding cavity, a second magnetic shielding cavity and a third magnetic shielding cavity, which are assembled together using stainless steel screws and pads without contacting each other, so that the residual magnetism of the reaction area is less than 1mGs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0025] Figure 2 It is a cross-sectional view of the overall structure of the present invention.

[0026] Figure 3 It is a side view of the fixed rod and electrostatic lens in the present invention.

[0027] Figure 4 Schematic diagram of the fixed rod and electrostatic lens in the present invention.

[0028] Figure 5 Schematic diagram of the structure of the electrode sheet in the present invention.

[0029] Figure 6 This is the momentum distribution image on the laser polarization plane captured by the present invention.

[0030] Reference numerals

[0031] Analysis chamber 1

[0032] Light intake window 11

[0033] Fixed rod 12

[0034] Fixing nut 13

[0035] Isolation washer 14

[0036] Gas injection mechanism 2

[0037] Cylinder 21

[0038] Intake pipe assembly 22

[0039] Hollow needle 23

[0040] 3D mobile platform 24

[0041] Vacuum mechanism 3

[0042] Image acquisition mechanism 4

[0043] MCP 41

[0044] Fluorescent screen 42

[0045] Camera 43

[0046] Reflector 5

[0047] Magnetic shielding mechanism 6

[0048] First magnetic shielding cavity 61

[0049] Second magnetic shielding cavity 62

[0050] The third magnetic shielding cavity 63

[0051] Drift tube 7

[0052] The first electrode group EpG1

[0053] The second electrode group EpG2

[0054] The third electrode group EpG3

[0055] Electrode sheet Ep DETAILED DESCRIPTION

[0056] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In the description of the present invention, it should be noted that the orientation or position relationship indicated by the terms "left side", "right side", "upper side", "lower side", "above", "below", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0057] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0058] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0059] Before describing the embodiments of the present invention, a brief introduction to the mechanism of a velocity imaging spectrometer is provided. In a velocity imaging spectrometer, sample molecules come into contact with a laser beam at its focal point and are ionized by the laser beam, generating electrons and ions. The target electrons or ions are then captured by an image acquisition mechanism 4 under the action of an electrostatic lens. During this process, the ionized region where the sample molecules come into contact with the laser beam's focal point is called the reaction zone. For purposes of illustration, although the ionization of sample molecules simultaneously generates both electrons and ions, only one can be captured in the same experiment. The polarization plane of a laser refers to the direction of oscillation of the laser's electric field. In a laser, the oscillation of the electric field can be confined to a specific plane, known as the polarization plane. For a linearly polarized laser, the electric field is confined to a single plane, along the direction of laser propagation. This means that if you observe the laser beam, you will see the electric field oscillating in a fixed plane, perpendicular to the direction of laser propagation. The polarization plane is an important parameter describing the polarization state of a laser beam because it determines the characteristics of the laser's interaction with matter, such as in materials processing, optical measurement, and communications.

[0060] The embodiment of the present invention provides a high-resolution coaxial velocity imaging device, referring to Figure 1 and Figure 2 , including an analysis chamber 1, a gas sampling mechanism 2, a vacuum mechanism 3, an electrostatic lens and an image acquisition mechanism 4; one end of the analysis chamber 1 is provided with a light inlet window 11, and a laser emitter is usually installed outside the analysis chamber 1, and the laser emitter is used to emit laser light, and the laser light enters the analysis chamber 1 through the light inlet window 11. The image acquisition mechanism 4 passes through one end of the analysis chamber 1 and is connected to the inner cavity of the analysis chamber 1; the gas sampling mechanism 2 and the vacuum mechanism 3 are both provided on the side wall of the analysis chamber 1 and are both connected to the inner cavity of the analysis chamber 1, the electrostatic lens is provided in the inner cavity of the analysis chamber 1, and the vacuum mechanism 2 can usually be a combination of a molecular pump and a dry pump. Continue reading Figure 3 The electrostatic lens includes a first electrode sheet group EpG1, a second electrode sheet group EpG2, and a third electrode sheet group EpG3, which are sequentially arranged along the axial direction of the analysis chamber 1. The first electrode sheet group EpG1 is close to the light-entry window 11. The first electrode sheet group EpG1, the second electrode sheet group EpG2, and the third electrode sheet group EpG3 each include a plurality of electrode sheets Ep, each of which is provided with a through hole. For illustration, the electrode sheets Ep are essentially the same, but are divided into a plurality of groups because of their different functions. The first electrode sheet group EpG1 is used to protect the uniform electric field generated by the second electrode sheet group EpG2, the second electrode sheet group EpG2 is used to form a uniform electric field, and the third electrode sheet group EpG3 is used to form a drift electric field. Figure 1 The gas injection mechanism 2 includes a gas cylinder 21, an air inlet pipe assembly 22 and a hollow needle 23 connected in sequence. The hollow needle 23 is located between the two electrode sheets Ep in the second electrode sheet group EpG2. In a specific embodiment, the gas injection mechanism 2 and the vacuum mechanism 3 are coaxially arranged. The axis is usually a diameter of the analysis chamber 1. In a preferred embodiment, as shown in FIG. Figure 1 As shown, in order to make the gas beam ejected from the hollow needle 23 hit the blades of the molecular pump (the vacuum mechanism 3 usually includes a molecular pump, and the molecular pump is connected to the analysis chamber 1), there is a certain offset between the molecular pump and the gas injection mechanism 2 in the axial direction of the analysis chamber 1. Figure 1In the through hole of the electrode sheet Ep in the second electrode sheet group EpG2, which is close to the third electrode sheet group EpG3, a metal mesh is further provided, and a reflector 5 is further provided on the metal mesh; the optical path of the laser, the reflector 5 and the image acquisition mechanism 4 are all located on the same axis, which is usually the central axis of the analysis cavity 1. As an explanation, the function of the reflector 5 is to reflect the laser beam. Generally speaking, the image acquisition mechanism 4 cannot withstand the intensity of the laser. Therefore, as mentioned in the background technology, most of the current laser incident directions are perpendicular to the axial direction of the analysis cavity 1 to avoid direct irradiation of the image acquisition mechanism 4 by the laser. Alternatively, although the momentum distribution image on the laser polarization plane can be captured in the coaxial velocity imaging mechanism, the conventional image acquisition mechanism 4 cannot withstand the energy of the laser, so a specially customized image acquisition mechanism 4 must be used. This type of image acquisition mechanism 4 is not only expensive but also very complex in structure. It is usually not adjusted after a single installation. Therefore, the role of the reflector 5 in the present invention is crucial. The reflector 5 can reflect the laser back to prevent the laser from directly irradiating the image acquisition mechanism 4. At the same time, because the optical path of the laser and the image acquisition mechanism 4 are located on the same axis, the momentum distribution image of the electron or ion on the polarization plane can be directly obtained. In summary, the optical path of the laser, the electrostatic lens and the image acquisition mechanism 4 in the present invention are located on the same axis, which is usually the central axis of the analysis cavity 1, and the electrode sheet Ep is also provided with a reflector 5 to reflect the laser, which can directly obtain the momentum distribution image of the electron or ion on the polarization plane; at the same time, the structure of the present invention is not complicated, and the overall modularization is adopted, which relatively simplifies the difficulty of installation, operation and debugging.

[0061] The high-resolution coaxial velocity imaging device provided by the embodiment of the present invention is described in detail. Figure 3 The inner cavity of the analysis chamber 1 is further provided with a fixing rod 12, which is sequentially passed through all the electrode sheets Ep. The fixing rod 12 is further provided with a plurality of fixing nuts 13 and a plurality of isolation washers 14, wherein two fixing nuts 13 are respectively located at the two ends of the fixing rod 12 and all the electrode sheets Ep are located between the two fixing nuts 13, and one or more isolation washers 14 are provided between adjacent electrode sheets Ep. In a specific embodiment, see Figure 3 and Figure 4 , including four fixing rods 12, which are simultaneously passed through all electrode sheets Ep. Preferably, the four fixing rods 12 can be used as the four vertices of a rectangle on a radial plane. The electrode sheet Ep is also provided with mounting holes that match the outer diameters of the four fixing rods 12. In terms of the radial plane facing the electrode sheet Ep, the mounting holes in each electrode sheet Ep are respectively located at the upper left, lower left, upper right and lower right of the electrode sheet Ep, and the through hole is located at the center of the electrode sheet Ep. For details, please refer to Figure 3 and Figure 4When installing the electrode piece Ep, first install a fixing nut 13 to one end of the fixing rod 12, then install the electrode piece Ep and the isolation gasket 14 in sequence, until all the electrode pieces Ep and the isolation gaskets 14 are installed, and then install another fixing nut 13 to the other end of the fixing rod 12. After the installation is completed, the electrode piece Ep is completely fixed on the fixing rod 12 and cannot move, and the centers of all the electrode pieces Ep are located on the same axis, which is usually the central axis of the analysis chamber 1. Here, we briefly explain how the fixing rod 12 is installed in the inner cavity of the analysis chamber 1, refer to Figure 2 and Figure 3 The end of the fixing rod 12 is connected to a multi-stage flange, and the flanges are assembled by screws and nuts, and the centers of all flanges are located on the same axis, which is usually the central axis of the analysis chamber 1. The outermost large flange in the multi-stage flange is installed to one end of the analysis chamber 1, so that the fixing rod 12 is in the inner cavity of the analysis chamber 1. In addition, some components in the image acquisition mechanism 4 (not mentioned above, please see below for details), such as: MCP41 and fluorescent screen 42 are located in the opening in the middle of the multi-stage flange.

[0062] In the high-resolution coaxial velocity imaging device provided by an embodiment of the present invention, the first electrode sheet group EpG1 includes N electrode sheets Ep, and the first electrode sheet group EpG1 is used to protect the uniform electric field generated by the second electrode sheet group EpG2; the second electrode sheet group EpG2 includes M electrode sheets Ep, and the second electrode sheet group EpG2 is used to form a uniform electric field; the third electrode sheet group EpG3 includes P electrode sheets Ep, and the third electrode sheet group EpG3 is used to form a drift electric field; wherein N, M and P satisfy the following relationship:

[0063] 4≤N+M+P≤16

[0064] 1≤N≤2, 2≤M≤8, 1≤P≤6.

[0065] In the high-resolution coaxial velocity imaging device provided in the embodiment of the present invention, following the above embodiment, the number of N is 2, the number of M is 8, and the number of P is 6, that is, the first electrode sheet group EpG1 includes 2 electrode sheets Ep, namely electrode sheet No. 1 Ep and electrode sheet No. 2 Ep, the second electrode sheet group EpG2 includes 8 electrode sheets Ep, namely electrode sheet No. 3 Ep to electrode sheet No. 11 Ep, the third electrode sheet group EpG3 includes 6 electrode sheets Ep, namely electrode sheet No. 12 Ep to electrode sheet No. 16 Ep, and the drift tube 7 is further provided in the electrode sheet No. 16, which can be specifically as follows Figure 3 Continue reading Figures 1 to 3The hollow needle 23 is located between electrode piece No. 5 Ep and electrode piece No. 6 Ep, one or more resistors are provided between each of electrode pieces No. 3 Ep to No. 10 Ep, a metal mesh is provided in the through holes of electrode piece No. 11 Ep and electrode piece No. 12 Ep, a metal mesh is also provided in the through hole of electrode piece No. 16 Ep near the end of the image acquisition mechanism 4, a reflector 5 is provided on the metal mesh of electrode piece No. 11 Ep, and electrode pieces No. 1 to 3 Ep and electrode pieces No. 11 to 16 Ep are all individually connected to external high-voltage connectors.

[0066] In the high-resolution coaxial velocity imaging device provided in an embodiment of the present invention, following the above-mentioned embodiment, the thickness of the isolation gasket 14 is 1-5 mm; and / or the thickness of the electrode sheet Ep is 1-136 mm; and / or the diameter of the opening in the electrode sheet Ep is 15-88 mm; and / or the transmittance of the metal mesh is ≥80%, the mesh size of the metal mesh is ≥180 mesh, and the wire diameter of the metal mesh is ≤0.015 mm; and / or the thickness of the reflector 5 is 1-3 mm, the diameter of the reflector 5 is 5-15 mm, and the diameter of the reflector 5 should be smaller than the diameter of the opening in the electrode sheet EP; and / or the fixing rod 12, fixing nut 13, and isolation gasket 14 are all made of ceramic. The above-mentioned design of the metal mesh and reflector 5 not only enables the laser to be smoothly reflected out of the analysis chamber 1, but also significantly reduces the interference and distortion of the electron or ion angular distribution caused by the support of the reflector 5 (i.e., the metal mesh).

[0067] In a specific embodiment, the thickness of electrode sheet No. 1 Ep to electrode sheet No. 3 is 1 mm, and the diameter of the through hole is 15 mm; the thickness of electrode sheet No. 4 Ep to electrode sheet No. 7 Ep is 1 mm, and the diameter of the through hole is 76 mm; the thickness of electrode sheet No. 8 Ep to electrode sheet No. 10 Ep is 1 mm, and the diameter of the through hole is 88 mm; the thickness of electrode sheet No. 11 Ep to electrode sheet No. 15 Ep is 4 mm, and the diameter of the through hole is 88 mm; the total thickness of electrode sheet No. 16 Ep is 131 mm, the thickness of drift tube 7 is 123 mm, and the thickness of electrode sheet No. 16 Ep at both ends of drift tube 7 is 8 mm. The through-hole diameter of electrode piece Ep No. 16 and the inner diameter of drift tube 7 are both 88mm. The through-holes of electrode piece Ep No. 11, electrode piece Ep No. 12 and electrode piece Ep No. 16 near image acquisition mechanism 4 are all provided with a metal mesh with a transmittance of 80%, a material of 316L stainless steel, a mesh size of 180 and a wire diameter of 0.015mm. The metal mesh can shield the adjacent electric field. A reflector 5 is provided on the metal mesh of electrode piece Ep No. 11. The reflector 5 has a diameter of 10mm and a thickness of 0.3mm. The substrate is silicon dioxide. The surface of the substrate is fully gold-plated, with 150nm of gold plating on the front and 20nm of gold plating on the side and back. In addition, refer to Figure 3, three isolation washers 14 are provided between electrode sheet No. 1 Ep and electrode sheet No. 2 Ep, two isolation washers 14 are provided between electrode sheet No. 2 Ep and electrode sheet No. 3 Ep, and only one ceramic washer is provided between every other two adjacent electrode sheets Ep, and the thickness of each ceramic washer is 3 mm. 10MΩ resistors are connected between electrode sheets No. 3 Ep to No. 5 Ep, and electrode sheets No. 6 Ep to No. 10 Ep, and two 10MΩ resistors are connected between electrode sheets No. 5 Ep to No. 6 Ep. When in use, a negative voltage is applied to electrode sheet No. 3 Ep and a positive voltage is applied to electrode sheet No. 10 Ep. By voltage division, a uniform electric field setting can be achieved between electrode sheet No. 3 Ep and electrode sheet No. 10 Ep, which can save 6 high-voltage electrode connectors and can conveniently control the voltage of all electrode sheets Ep. Furthermore, by performing simulation in a computer, the voltage value required for each of the 16 electrode sheets Ep can be obtained. For illustration, the trajectory of the product particles is controlled by an electrostatic lens. By adjusting the voltage applied to the 16 electrodes Ep, the trajectory of the electrons or ions can be controlled, essentially changing the operating mode of the electrostatic lens to achieve the goal of focusing the electrons or ions. The voltage of each electrode in this embodiment is carefully designed to more precisely control the trajectory of electrons and ions, with a resolution of 1% @ 60eV.

[0068] 4) In the high-resolution coaxial velocity imaging device provided in the embodiment of the present invention, refer to Figure 1 and Figure 2A magnetic shielding mechanism 6 is also provided in the inner cavity of the analysis cavity 1. The magnetic shielding mechanism 6 includes a first magnetic shielding cavity 61, a second magnetic shielding cavity 62 and a third magnetic shielding cavity 63 arranged in sequence from the inside to the outside; the electrostatic lens is arranged in the first magnetic shielding cavity 61. Specifically, the central axes of the first magnetic shielding cavity 61, the second magnetic shielding cavity 62 and the third magnetic shielding cavity 63 all coincide with the central axis of the analysis cavity 1. The inner diameters of the first magnetic shielding cavity 61, the second magnetic shielding cavity 62 and the third magnetic shielding cavity 63 decrease step by step, and are assembled together with screws and pads made of stainless steel or aluminum alloy. The magnetic flux lines do not flow between each other. The material of the first magnetic shielding cavity 61, the second magnetic shielding cavity 62 and the third magnetic shielding cavity is generally Permalloy (1J85). Permalloy (1J85) has high initial magnetic permeability and maximum magnetic permeability, high saturation magnetic induction intensity and low coercive force under weak magnetic fields, and its magnetic properties are less sensitive to external interference factors. Therefore, it is widely used in magnetic field shielding engineering design. As an illustration, in addition to the electric field, the product particles emitted by the source region are not only pulled by the electric field of the electrostatic lens on their way to the detector, but are also disturbed by the stray magnetic field in space (such as the Earth's magnetic field and the magnetic field generated by electrical appliances). For high-resolution spectrometers, the influence of these stray magnetic fields on the flight trajectory of photoelectrons cannot be ignored. Therefore, in the high-resolution high-speed imaging device provided by the present invention, the electrode piece Ep, the fixing rod 12, the fixing nut 13 and the isolation washer 14 are all made of non-magnetic and vacuum-friendly materials, such as aluminum alloy, stainless steel or ceramic. Preferably, the fixing rod 12, the isolation washer 14 and the fixing nut 13 are made of ceramic material, and the electrode piece Ep is made of aluminum alloy. The first magnetic shielding cavity, the second magnetic shielding cavity and the third magnetic shielding cavity in the present invention are assembled together using stainless steel screws and pads between each other, and do not contact each other, so that the residual magnetism of the reaction area is less than 1mGs.

[0069] In the high-resolution coaxial velocity imaging device provided by the embodiment of the present invention, refer to Figure 1The gas injection mechanism 2 also includes a three-dimensional movable platform 24. The gas inlet pipe assembly 22 includes a micro-leak valve, a 1 / 4-inch tube, and a 1 / 8-inch tube that are sequentially connected and communicated. One end of the 1 / 8-inch tube is connected and communicated with a hollow needle 23. The three-dimensional movable platform 24 is located outside the 1 / 4-inch tube and is connected to the 1 / 4-inch tube. The three-dimensional movable platform 24 can generally be a three-dimensional movable platform 24 with model number TTX63-100-100-S from Kurt J. Lesker. The 1 / 4-inch tube can be welded to the flange of the three-dimensional movable platform 24. As an illustration, the micro-leak valve and gas cylinder 21 are located outside the analysis chamber 1. When the gas injection mechanism 2 is in use, sample molecules flow out of the gas cylinder 21, and the gas flow rate is controlled by the micro-leak valve. After passing through the 1 / 4-inch tube and the 1 / 8-inch tube, the sample molecules are sprayed into the analysis chamber 1 from the end of the hollow needle 23. The background vacuum degree in the inner cavity of the analysis chamber 1 can reach 5×10 -10 mbar, so the gas ejected from the end of the hollow needle 23 enters the inner cavity of the analysis chamber 1 by adiabatic expansion. The material of the analysis chamber 1 is generally stainless steel, preferably 316L stainless steel. In a specific embodiment, the hollow needle 23 is made of stainless steel and has an outer diameter of 0.2 mm and an inner diameter of 0.09 mm.

[0070] In the high-resolution coaxial velocity imaging device provided by the embodiment of the present invention, refer to Figure 1 and Figure 2 The image acquisition mechanism 4 includes an MCP41, a fluorescent screen 42, and a camera 43, which are sequentially arranged along the axial direction of the analysis chamber 1. The MCP41 is close to the third electrode sheet group EpG3. The gas ejected from the end of the hollow needle 23 intersects the laser perpendicularly at the laser focus (the reaction zone, usually located between electrode sheets Ep 5 and Ep 6). The sample molecules are ionized by the laser, generating electrons and ions. The target electrons or ions are focused on the MCP41 under the action of the electrostatic lens. The charged particles collide with the MCP41, and the signal is amplified. The amplified signal bombards the fluorescent screen 42 behind the MCP41, generating fluorescent bright spots. The distribution image of these bright spots is captured and recorded by the camera 43. This is the original image of the sample produced by the laser ionization. As an illustration, the MCP41 is a microchannel plate, which is a particle multiplication detector with high spatial resolution.

[0071] The present invention also provides a method for using a high-resolution coaxial velocity imaging device, comprising at least the following steps:

[0072] 1) The laser enters the inner cavity of the analysis chamber 1 through the light inlet window 11 and ionizes the sample molecules injected by the gas injection device 2 in the reaction zone, generating electrons and ions;

[0073] 2) The sample molecules are ionized to generate electrons and ions, which are focused on the image acquisition mechanism 4 under the action of the electrostatic lens and are collected by the image acquisition mechanism 4. Figure 6 This is the momentum distribution image of electrons or ions captured by the present invention on the polarization plane of the laser.

[0074] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A high-resolution coaxial velocity imaging device, characterized by: It includes an analysis chamber (1), a gas sampling mechanism (2), a vacuum mechanism (3), an electrostatic lens, and an image acquisition mechanism (4); One end of the analysis chamber (1) is provided with a light-inlet window (11) suitable for allowing laser light to pass through; the image acquisition mechanism (4) passes through one end of the analysis chamber (1) and is connected to the inner cavity of the analysis chamber (1); the gas injection mechanism (2) and the vacuum mechanism (3) are both provided on the side wall of the analysis chamber (1) and are both connected to the inner cavity of the analysis chamber (1); the electrostatic lens is provided in the inner cavity of the analysis chamber (1); The electrostatic lens comprises a first electrode sheet group (EpG1), a second electrode sheet group (EpG2) and a third electrode sheet group (EpG3) which are sequentially arranged along the axial direction of the analysis cavity (1), wherein the first electrode sheet group (EpG1) is close to the light entrance window (11); the first electrode sheet group (EpG1), the second electrode sheet group (EpG2) and the third electrode sheet group (EpG3) each comprise a plurality of electrode sheets (Ep), and each of the electrode sheets (Ep) is provided with a through hole; The gas sampling mechanism (2) comprises a gas cylinder (21), an air inlet pipe assembly (22), and a hollow needle (23) connected in sequence, wherein the hollow needle (23) is located between two electrode sheets (Ep) in the second electrode sheet group (EpG2); A metal mesh is further provided in the through hole of the electrode sheet (Ep) in the second electrode sheet group (EpG2) close to the third electrode sheet group (EpG3), and a reflector (5) is further provided on the metal mesh; the optical path of the laser, the reflector (5) and the image acquisition mechanism (4) are located on the same axis; The first electrode sheet group (EpG1) includes N electrode sheets (Ep), and the first electrode sheet group (EpG1) is used to protect a uniform electric field; the second electrode sheet group (EpG2) includes M electrode sheets (Ep), and the second electrode sheet group (EpG2) is used to form a uniform electric field; the third electrode sheet group (EpG3) includes P electrode sheets (Ep), and the third electrode sheet group (EpG3) is used to form a drift electric field; wherein N, M and P satisfy the following relationship The first electrode sheet group (EpG1) includes two electrode sheets (Ep), namely electrode sheet No. 1 (Ep) and electrode sheet No. 2 (Ep).

2. The high-resolution coaxial velocity imaging device according to claim 1, characterized in that: A fixing rod (12) is further provided in the inner cavity of the analysis chamber (1), and the fixing rod (12) is sequentially passed through all the electrode sheets (Ep); a plurality of fixing nuts (13) and a plurality of isolation washers (14) are further provided on the fixing rod (12), wherein two fixing nuts (13) are respectively located at the two ends of the fixing rod (12) and all the electrode sheets (Ep) are located between the two fixing nuts (13), and one or more isolation washers (14) are provided between adjacent electrode sheets (Ep).

3. The high-resolution coaxial velocity imaging device according to claim 2, characterized in that: The thickness of the isolation gasket (14) is 1-5 mm; and / or the thickness of the electrode sheet (Ep) is 1-136 mm; and / or the diameter of the opening in the electrode sheet (Ep) is 15-88 mm; and / or the transmittance of the metal mesh is ≥80%, the mesh number of the metal mesh is ≥180 mesh, and the wire diameter of the metal mesh is ≤0.015 mm; and / or the thickness of the reflector (5) is 1-3 mm, and the diameter of the reflector (5) is 5-15 mm; and / or the materials of the fixing rod (12), the fixing nut (13) and the isolation gasket (14) are all ceramic.

4. The high-resolution coaxial velocity imaging device according to claim 3, characterized in that: The second electrode sheet group (EpG2) includes eight electrode sheets (Ep), namely electrode sheet No. 3 (Ep) to electrode sheet No. 11 (Ep); the third electrode sheet group (EpG3) includes six electrode sheets (Ep), namely electrode sheet No. 12 (Ep) to electrode sheet No. 16 (Ep); the electrode sheet No. 16 (Ep) is also provided with a drift tube (7); The hollow needle (23) is located between electrode sheet No. 5 (Ep) and electrode sheet No. 6 (Ep); one or more resistors are provided between each of electrode sheet No. 3 (Ep) to electrode sheet No. 10 (Ep); metal meshes are provided in the through holes of electrode sheet No. 11 (Ep) and electrode sheet No. 12 (Ep); a metal mesh is also provided in the through hole of electrode sheet No. 6 (Ep) near one end of the image acquisition mechanism 4; the reflector (5) is provided on the metal mesh of electrode sheet No. 11 (Ep); electrode sheet No. 1 (Ep) to electrode sheet No. 3 (Ep) and electrode sheet No. 11 (Ep) to electrode sheet No. 16 (Ep) are all individually connected to high-voltage connectors.

5. The high-resolution coaxial velocity imaging device according to claim 4, characterized in that: The thickness of electrode sheet No. 1 (Ep) to electrode sheet No. 3 (Ep) is 1mm, and the diameter of the through hole is 15mm; the thickness of electrode sheet No. 8 (Ep) to electrode sheet No. 10 (Ep) is 1mm, and the diameter of the through hole is 88mm; the thickness of electrode sheet No. 11 (Ep) to electrode sheet No. 15 (Ep) is 4mm, and the diameter of the through hole is 88mm; the total thickness of electrode sheet No. 16 (Ep) is 131mm, the thickness of drift tube (7) is 123mm, and the No. 16 electrode sheet at both ends of drift tube (7) is 131mm. The thickness of the electrode sheet (Ep) is 8 mm, the through-hole diameter of the No. 16 electrode sheet (Ep) and the inner diameter of the drift tube (7) are both 88 mm; the transmittance of the metal mesh is 80%, the material of the metal mesh is 316L stainless steel, the mesh number of the metal mesh is 180 mesh, and the wire diameter of the metal mesh is 0.015 mm; the diameter of the reflector (5) is 10 mm, the thickness is 0.3 mm, the substrate of the reflector (5) is silicon dioxide, and the surface of the substrate is fully gold-plated, the front side is gold-plated with 150 nm, and the side and back sides are gold-plated with 20 nm.

6. The high-resolution coaxial velocity imaging device according to claim 1, characterized in that: A magnetic shielding mechanism (6) is further provided in the inner cavity of the analysis cavity (1), and the magnetic shielding mechanism (6) comprises a first magnetic shielding cavity (61), a second magnetic shielding cavity (62), and a third magnetic shielding cavity (63) arranged in sequence from the inside to the outside; the electrostatic lens is provided in the first magnetic shielding cavity (61).

7. The high-resolution coaxial velocity imaging device according to claim 1, characterized in that: The gas injection mechanism (2) further includes a three-dimensional movable platform (24), the gas inlet pipe assembly (22) includes a 1 / 4-inch tube and a 1 / 8-inch tube that are sequentially connected and communicated, one end of the 1 / 8-inch tube is connected and communicated with the hollow needle (23); the three-dimensional movable platform (24) is arranged outside the 1 / 4-inch tube and is connected to the 1 / 4-inch tube.

8. The high-resolution coaxial velocity imaging device according to claim 1, characterized in that: The image acquisition mechanism (4) comprises an MCP (41), a fluorescent screen (42), and a camera (43) arranged in sequence along the axial direction of the analysis cavity (1), and the MCP (41) is close to the third electrode sheet group (EpG3).

9. A method for using the high-resolution coaxial velocity imaging device according to any one of claims 1 to 8, characterized in that: It includes at least the following steps: The laser enters the inner cavity of the analysis chamber (1) through the light entrance window (11), and ionizes the sample molecules injected by the gas injection mechanism (2) in the reaction zone to generate electrons and ions; The sample molecules are ionized to generate electrons and ions, which are focused on the image acquisition mechanism (4) under the action of the electrostatic lens and are collected by the image acquisition mechanism (4).

Images