A laser desorption and ionization device

Abstract

The present invention relates to the technical field of mass spectrometers, and more specifically, to a laser desorption post-ionization device comprising a laser sputtering chamber, a laser light source assembly, a vacuum ultraviolet light source, a repeller electrode, a photocathode, a ring magnet, a sample target, an extraction electrode, and a mass spectrometer. The present invention utilizes a vacuum ultraviolet light source to illuminate the photocathode. Photoelectrons generated by the photoelectric effect on the surface of the photocathode acquire high energy under the influence of magnetic and electric fields. These electrons are then used to ionize the large number of neutral particle plumes generated by laser desorption, thereby addressing the severe matrix effect associated with laser ionization and significantly improving ionization sensitivity.

Description

Technical Field

[0001] The invention relates to the technical field of mass spectrometers, in particular to a laser desorption and post-ionization device. Background Art

[0002] The absolute ionization efficiency of samples in laser sputtering ionization within a limited sampling volume is insufficient, with over 99.9% of the sample being neutral species, and matrix effects are also a significant source of interference. The development of neutral particle post-ionization technology has become an effective solution to reduce the impact of matrix effects and improve ionization efficiency.

[0003] Photoelectron ionization occurs when vacuum ultraviolet light photons strike a metal electrode, generating photoelectrons that are accelerated by an electric field and then collide with sample molecules, producing a spectrum similar to electron ionization. This patented invention applies photoelectron ionization to laser desorption post-ionization, proposing a novel laser desorption post-ionization technique. Summary of the Invention

[0004] In view of the problems of insufficient laser desorption ionization efficiency and serious matrix effect, the present invention aims to provide a laser desorption and post-ionization device.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] A laser desorption and post-ionization device comprises a laser sputtering cavity, a laser light source assembly, a vacuum ultraviolet light source, a repeller electrode, a photocathode, a ring magnet, a sample target, an extraction electrode and a mass spectrometer;

[0007] The extraction electrode is insulated and mounted on the laser sputtering chamber. The mass spectrometer is connected to the portion of the extraction electrode located outside the laser sputtering chamber. A conical channel is provided on the extraction electrode. The opening at one end with a larger diameter of the conical channel is opposite to the sample input end of the mass spectrometer, and the opening at one end with a smaller diameter of the conical channel is located inside the laser sputtering chamber.

[0008] The repeller electrode and the photocathode are respectively installed inside the laser sputtering chamber, the photocathode and the repeller electrode are parallel to each other, the repeller electrode is located on a side away from the extraction electrode, a through hole A is formed on the repeller electrode, the photocathode is located on a side close to the extraction electrode, a through hole B is formed on the photocathode, the annular magnet is installed on a side of the photocathode close to the repeller electrode and a through hole C is formed on the photocathode, the aperture of the through hole C is larger than the aperture of the through hole B, a gap is formed between the repeller electrode and the annular magnet, the vacuum ultraviolet light source is installed on a side of the repeller electrode away from the photocathode, the axial centerline of the through hole A of the repeller electrode, the axial centerline of the through hole B of the photocathode, the axial centerline of the through hole C of the annular magnet, and the axial centerline of the tapered channel of the extraction electrode are all collinear, and light emitted by the vacuum ultraviolet light source passes through the through holes A and C and irradiates the surface of the photocathode;

[0009] The sample target is arranged inside the laser sputtering cavity, the laser light emitted by the laser light source assembly irradiates the sample target, and the focal position of the laser light emitted by the laser light source assembly on the sample target corresponds to the gap position between the repeller electrode and the annular magnet.

[0010] The laser sputtering cavity is provided with an air extraction port and an injection pipeline, the injection pipeline is connected to an external inert gas source, and the air extraction port is provided with a molecular pump.

[0011] A vacuum gauge is also provided on the laser sputtering cavity.

[0012] The vacuum ultraviolet light source adopts a gas discharge lamp light source or a laser light source.

[0013] The sample target is installed in the laser sputtering cavity through a three-dimensional moving platform.

[0014] The laser light source assembly includes a laser, a reflector, a lens and a quartz window. The laser, reflector and lens are respectively arranged on the outside of the laser sputtering cavity. The quartz window is arranged on the laser sputtering cavity corresponding to the sample target. The laser emitted by the laser is reflected by the reflector and sequentially passes through the lens and the quartz window to irradiate the sample target.

[0015] The advantages and positive effects of the present invention are:

[0016] This method uses photoelectrons to efficiently secondary ionize a neutral gas plume, decoupling the sputtering process from the ionization process, effectively eliminating the matrix effect and improving ionization efficiency. This method is not limited by operating gas pressure, is easy to control, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention.

[0018] In the figure: 1 is the laser sputtering chamber, 2 is the vacuum ultraviolet light source, 3 is the repeller electrode, 4 is the photocathode, 5 is the ring magnet, 6 is the sample target, 7 is the extraction electrode, 8 is the injection pipeline, 9 is the molecular pump, 10 is the vacuum gauge, 11 is the three-dimensional moving platform, 12 is the laser, 13 is the reflector, 14 is the lens, and 15 is the quartz window. DETAILED DESCRIPTION

[0019] The following is combined with Figure 1 The present invention is described in further detail.

[0020] A laser desorption and subsequent ionization device, such as Figure 1 As shown, this embodiment includes a laser sputtering chamber 1, a laser light source assembly, a vacuum ultraviolet light source 2, a repeller electrode 3, a photocathode 4, a ring magnet 5, a sample target 6, an extraction electrode 7 and a mass spectrometer. In this embodiment, the vacuum ultraviolet light source 2 adopts a deuterium lamp. The mass spectrometer can adopt a time-of-flight mass spectrometer, a quadrupole mass spectrometer or an ion trap mass spectrometer. In this embodiment, the mass spectrometer adopts a time-of-flight mass spectrometer. Figure 1 The direction indicated by the middle arrow is the location of the mass spectrometer.

[0021] Extraction electrode 7 is insulated and mounted on laser sputtering chamber 1. The mass spectrometer is connected to the portion of extraction electrode 7 located outside of the laser sputtering chamber 1. Extraction electrode 7 has a tapered channel, with the larger end of the channel facing the sample input of the mass spectrometer and the smaller end of the channel located within the laser sputtering chamber 1. The connection structure between extraction electrode 7 and the mass spectrometer in this embodiment is conventional.

[0022] A repeller electrode 3 and a photocathode 4 are respectively installed inside the laser sputtering chamber 1. The photocathode 4 and the repeller electrode 3 are parallel to each other. The repeller electrode 3 is located on the side away from the extraction electrode 7. A through hole A is formed on the repeller electrode 3. The photocathode 4 is located on the side close to the extraction electrode 7. A through hole B is formed on the photocathode 4. An annular magnet 5 is installed on the side of the photocathode 4 close to the repeller electrode 3 and has a through hole C. The annular magnet 5 is also parallel to the repeller electrode 3. The aperture of through hole C is larger than the aperture of through hole B. There is a gap between the repeller electrode 3 and the annular magnet 5. The vacuum ultraviolet light source 2 is installed on the side of the repeller electrode 3 away from the photocathode 4. The axial centerline of through hole A of the repeller electrode 3, the axial centerline of through hole B of the photocathode 4, the axial centerline of through hole C of the annular magnet 5, and the axial centerline of the tapered channel of the extraction electrode 7 are all collinear. Light emitted by the vacuum ultraviolet light source 2 passes through through hole A and through hole C and is irradiated on the surface of the photocathode 4. The repelling electrode 3 is a circular flat electrode, with a central aperture of 2-15 mm (in this embodiment, 6 mm). The photocathode 4 is a circular flat electrode, with a central aperture of 2-15 mm (in this embodiment, 3 mm). The annular magnet 5 is a flat annular magnet.

[0023] The sample target 6 is disposed within the laser sputtering chamber 1. The laser light emitted by the laser light source assembly irradiates the sample target 6, and the focal position of the laser light emitted by the laser light source assembly on the sample target 6 corresponds to the position of the gap between the repeller electrode 3 and the annular magnet 5. In this embodiment, the sample target 6 is placed perpendicular to the repeller electrode 3.

[0024] Specifically, in this embodiment, the laser sputtering chamber 1 is provided with an air pump and a sampling line 8, the sampling line 8 is connected to an external inert gas source, a molecular pump 9 is provided on the air pump, and a vacuum gauge 10 is provided on the laser sputtering chamber 1. In this embodiment, the molecular pump 9 and the vacuum gauge 10 are both commercially available products. In this embodiment, the sampling line 8 is connected to an external inert gas source to introduce an inert gas such as helium. The internal pressure of the entire laser sputtering chamber 1 is controlled at 10 by controlling the inert gas flow rate and adjusting the molecular pump 9 switch. -4 -1000 Pa. In this embodiment, the internal pressure of the entire laser sputtering chamber 1 is controlled at 0.3 Pa. The internal pressure of the laser sputtering chamber 1 is detected by a vacuum gauge 10 .

[0025] Specifically, in this embodiment, the sample target 6 is installed in the laser sputtering chamber 1 through a three-dimensional moving platform 11. In this embodiment, the three-dimensional moving platform 11 is a commercial product and its movement is controlled by an external controller. Figure 1As shown, the sample target 6 is fixed on the surface of the three-dimensional moving platform 11. The three-dimensional moving platform 11 can move the position of the sample target 6 in the X, Y, and Z directions with a moving accuracy of 1 μm, which is convenient for adjusting the position of the laser irradiating the sample target 6.

[0026] Specifically, the laser light source assembly in this embodiment includes a laser 12, a reflector 13, a lens 14, and a quartz window 15. The laser 12, reflector 13, and lens 14 are respectively disposed outside the laser sputtering chamber 1. The quartz window 15 is disposed on the laser sputtering chamber 1 at a location corresponding to the sample target 6. The laser light emitted by the laser 12 is reflected by the reflector 13 and sequentially passes through the lens 14 and the quartz window 15 to irradiate the sample target 6. In this embodiment, the laser 12, reflector 13, and lens 14 are all commercially available products. The configuration of the quartz window 15 is also conventional, making it easy to adjust according to the experimental location.

[0027] Working principle:

[0028] The laser light emitted by the laser light source assembly irradiates the sample target 6 and sputters to produce a neutral plume. The vacuum ultraviolet light emitted by the vacuum ultraviolet light source 2 irradiates the photocathode 4 and generates photoelectrons, which ionize the neutral plume under the action of the electric field and magnetic field between the repeller electrode 3 and the photocathode 4 to produce high-intensity sample ions. The ions are then transmitted to the mass spectrometer for detection via the extraction electrode 7 under the action of the electric field. The present invention uses the vacuum ultraviolet light source 2 to irradiate the photocathode 4. The photoelectrons generated by the photoelectric effect on the surface of the photocathode 4 obtain higher energy under the action of the magnetic field and electric field, and are used to ionize a large number of neutral particle plumes generated by laser desorption, thereby solving the serious matrix effect of laser ionization and greatly improving the sensitivity of ionization.

Claims

1. A laser desorption and post-ionization device, characterized in that: It comprises a laser sputtering cavity (1), a laser light source assembly, a vacuum ultraviolet light source (2), a repelling electrode (3), a photocathode (4), a ring magnet (5), a sample target (6), an extraction electrode (7) and a mass spectrometer; The extraction electrode (7) is insulated and mounted on the laser sputtering cavity (1); the mass spectrometer is connected to the portion of the extraction electrode (7) located outside the laser sputtering cavity (1); a conical channel is provided on the extraction electrode (7); an opening at one end with a larger diameter of the conical channel is opposite to a sample input end of the mass spectrometer; and an opening at one end with a smaller diameter of the conical channel is located inside the laser sputtering cavity (1); The repelling electrode (3) and the photocathode (4) are respectively installed inside the laser sputtering cavity (1), the photocathode (4) and the repelling electrode (3) are parallel to each other, the repelling electrode (3) is located on the side away from the extraction electrode (7), and a through hole A is provided on the repelling electrode (3), the photocathode (4) is located on the side close to the extraction electrode (7), and a through hole B is provided on the photocathode (4), the annular magnet (5) is installed on the side surface of the photocathode (4) close to the repelling electrode (3) and a through hole C is provided, and the aperture of the through hole C is larger than the through hole (7). The aperture of the through hole B, there is a gap between the repelling electrode (3) and the annular magnet (5), the vacuum ultraviolet light source (2) is installed on the side of the repelling electrode (3) away from the photocathode (4), the axial center line of the through hole A of the repelling electrode (3), the axial center line of the through hole B of the photocathode (4), the axial center line of the through hole C of the annular magnet (5) and the axial center line of the tapered hole of the extraction electrode (7) are all collinear, and the light emitted by the vacuum ultraviolet light source (2) passes through the through hole A and the through hole C and is irradiated on the surface of the photocathode (4); The sample target (6) is arranged inside the laser sputtering cavity (1), the laser light emitted by the laser light source assembly irradiates the sample target (6), and the focal position of the laser light emitted by the laser light source assembly on the sample target (6) corresponds to the position of the gap between the repelling electrode (3) and the annular magnet (5).

2. The laser desorption and post-ionization device according to claim 1, characterized in that: The laser sputtering chamber (1) is provided with an air extraction port and an injection pipeline (8), the injection pipeline (8) is connected to an external inert gas source, and a molecular pump (9) is provided on the air extraction port.

3. The laser desorption and post-ionization device according to claim 1, characterized in that: A vacuum gauge (10) is also provided on the laser sputtering cavity (1).

4. The laser desorption and post-ionization device according to claim 1, characterized in that: The vacuum ultraviolet light source (2) adopts a gas discharge lamp light source or a laser light source.

5. The laser desorption and post-ionization device according to claim 1, characterized in that: The sample target (6) is installed in the laser sputtering chamber (1) via a three-dimensional moving platform (11).

6. The laser desorption and post-ionization device according to claim 1, characterized in that: The laser light source assembly comprises a laser (12), a reflector (13), a lens (14) and a quartz window (15). The laser (12), the reflector (13) and the lens (14) are respectively arranged on the outside of the laser sputtering cavity (1). The quartz window (15) is arranged on the laser sputtering cavity (1) at a position corresponding to the sample target (6). The laser light emitted by the laser (12) is reflected by the reflector (13) and sequentially passes through the lens (14) and the quartz window (15) to irradiate the sample target (6).

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