JP7451344B2 - Vacuum ultraviolet one-photon ionization mass spectrometer - Google Patents

Description

The present invention relates to a vacuum ultraviolet one-photon ionization mass spectrometer.

Generally, exhaust gas discharged from factories etc. contains trace amounts of components such as aromatic compounds. When considering environmental impact, it is important to detect and quantify such trace amounts of components in exhaust gas.

As a method for measuring components in a gas, a vacuum ultraviolet one-photon ionization mass spectrometry method has been proposed in which vacuum ultraviolet light is irradiated onto a sample to ionize the sample with one photon, and mass spectrometry is performed. For example, Patent Document 1 proposes a measurement system and a measurement method for monitoring molecular species in an environmentally hazardous gas, which combines a one-photon ionization mass spectrometer using a laser beam and an infrared spectrometer.

Further, Patent Document 2 proposes a time-of-flight mass spectrometer in which ions orbit in an arcuate trajectory in order to obtain high mass resolution.

Japanese Patent Application Publication No. 2013-174558 Japanese Patent Application Publication No. 2011-146180

In the one-photon ionization mass spectrometry described in Patent Document 1 as described above, so-called soft ionization, which can suppress molecular cleavage during ionization, is possible, and molecular species can be identified relatively easily. However, in the one-photon ionization mass spectrometry described in Patent Document 1, mass spectrometry is performed using a general time-of-flight mass spectrometer, and higher mass resolution is desired.

On the other hand, the time-of-flight mass spectrometer described in Patent Document 2 can achieve a long flight time because ions orbit in an arcuate trajectory, and thereby has high mass resolution. However, the time-of-flight mass spectrometer described in Patent Document 2 employs an electron ionization method or a chemical ionization method as an ionization method, and fragmentation of target molecules is likely to occur during ionization. Such fragmentation creates many detection peaks and complicates analysis when analyzing an unknown sample composition.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a vacuum ultraviolet one-photon ionization mass spectrometer that is capable of soft ionization and has high mass resolution. It's about doing.

In order to solve the above-mentioned problems, the present inventors first attempted to use a vacuum ultraviolet one-photon ionization device as an ion source and combine this with a multi-turn time-of-flight mass spectrometer as a mass spectrometer. However, when these ion sources and mass spectrometers were simply combined, a problem was encountered in that the devices did not work.

The inventors investigated the cause of this problem and found that vacuum ultraviolet rays are generally generated by converting ultraviolet rays, but the intensity of the ultraviolet rays that were not used for conversion was high, and this caused the ion source to enter the ion source. It has also been found that this can have an adverse effect on the ion source. Then, in order to block such ultraviolet rays, it was discovered that two apertures should be provided, and the present invention described below was conceived.
The gist of the present invention, which was completed based on the above findings, is as follows.

(1) A vacuum ultraviolet ray generator that generates a vacuum ultraviolet laser;
an ion generation unit that ionizes the sample by one photon using the vacuum ultraviolet laser to generate target ions;
a multi-orbit time-of-flight mass spectrometer that detects the target ions and measures the mass of the target ions,
The vacuum ultraviolet ray generation section includes a conversion section that converts the ultraviolet laser into the vacuum ultraviolet laser, and a condensing lens that focuses the vacuum ultraviolet laser and introduces it into the ion generation section,
The ion generating section is
an ionization unit that irradiates the sample with the vacuum ultraviolet laser and pushes out the one-photon ionized target ions to the multi-turn time-of-flight mass spectrometry unit;
a first aperture disposed between the ionization section and the condensing lens and along the optical axis of the vacuum ultraviolet laser;
A vacuum ultraviolet one-photon ionization mass spectrometer, comprising a second aperture disposed between the ionization section and the first aperture and along the optical axis of the vacuum ultraviolet laser.
(2) The vacuum ultraviolet one-photon ionization mass spectrometer according to (1), wherein the second aperture is arranged adjacent to the ionization section.
(3) The vacuum ultraviolet one-photon ionization mass spectrometer according to (1) or (2), wherein the second aperture is grounded.
(4) Any one of (1) to (3), wherein the second aperture has a surface facing the first aperture that is inclined with respect to the optical axis of the vacuum ultraviolet laser. The vacuum ultraviolet one-photon ionization mass spectrometer described in .
(5) The vacuum ultraviolet one-photon ionization mass spectrometer according to (4), wherein the ion generating section includes a view port through which the ultraviolet laser reflected by the inclined surface can pass.
(6) The vacuum ultraviolet one-photon ionization mass spectrometer according to (4) or (5), further comprising an ultraviolet detection section that detects the ultraviolet laser reflected by the inclined surface of the second aperture.
(7) The vacuum according to (6), which has an adjustment mechanism that adjusts the optical axis and/or light amount of the vacuum ultraviolet laser according to the position and/or intensity of the ultraviolet laser detected by the ultraviolet detection unit. Ultraviolet one-photon ionization mass spectrometer.
(8) The optical axis of the vacuum ultraviolet laser is perpendicular to a plane formed by the orbit of the target ion in the multi-orbit time-of-flight mass spectrometer, according to any one of (1) to (7). vacuum ultraviolet one-photon ionization mass spectrometer.
(9) According to any one of (1) to (8), the ionization unit further includes an electron gun capable of irradiating the sample with an electron beam perpendicular to the optical axis of the vacuum ultraviolet laser. The vacuum ultraviolet one-photon ionization mass spectrometer described above.

According to the present invention, it is possible to provide a vacuum ultraviolet one-photon ionization mass spectrometer that is capable of soft ionization and has high mass resolution.

1 is a schematic diagram schematically showing an outline of a vacuum ultraviolet one-photon ionization mass spectrometer according to an embodiment of the present invention. FIG. 2 is an enlarged schematic diagram illustrating the configuration of an ion generation section of the vacuum ultraviolet one-photon ionization mass spectrometer shown in FIG. 1. FIG. FIG. 2 is a schematic diagram of the vacuum ultraviolet one-photon ionization mass spectrometer shown in FIG. 1 taken along the a-a line.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that, in this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals and redundant explanation will be omitted.

<1. Configuration of vacuum ultraviolet one-photon ionization mass spectrometer>
First, a vacuum ultraviolet one-photon ionization mass spectrometer according to this embodiment will be described. FIG. 1 is a schematic diagram schematically showing the outline of a vacuum ultraviolet one-photon ionization mass spectrometer according to an embodiment of the present invention, and FIG. 2 is an ion generating section of the vacuum ultraviolet one-photon ionization mass spectrometer shown in FIG. FIG. 3 is a schematic diagram of the vacuum ultraviolet one-photon ionization mass spectrometer shown in FIG. 1 taken along the a-a line. Note that in the drawings, each component is enlarged or reduced as appropriate for ease of explanation, and actual dimensions are not shown. Further, in each figure, for ease of explanation, members unnecessary for the explanation are omitted. Furthermore, regarding the movement of ultraviolet lasers, vacuum ultraviolet lasers, and substances such as samples in each figure, only the typical directions of movement, such as the optical axes of ultraviolet lasers and vacuum ultraviolet lasers, are shown, and detailed spread, etc. Description has been omitted.

The vacuum ultraviolet one-photon ionization mass spectrometer 1 shown in FIG. have.

The vacuum ultraviolet ray generator 10 generates a vacuum ultraviolet ray (VUV) laser. The vacuum ultraviolet ray generator 10 includes a light guide lens 11 that guides the pulsed ultraviolet laser UV oscillated from the solid-state laser oscillator to a converter 13, and a converter 13 that converts the ultraviolet laser UV into a vacuum ultraviolet VUV laser. , and a condensing lens 15 that condenses the vacuum ultraviolet VUV laser converted in the converting section 13 and introduces it into the ion generating section 20.

The light guide lens 11 introduces pulsed ultraviolet laser UV of a solid-state laser oscillated by a solid-state laser oscillation unit (not shown) into the conversion unit 13 . The light guiding lens 11 condenses the ultraviolet laser UV so that the ultraviolet laser UV converges on a target area within the conversion unit 13 . The light guide lens 11 is made of, for example, synthetic quartz, magnesium fluoride, or the like. In addition, examples of solid-state lasers include YAG lasers and the like. The pulsed ultraviolet laser UV can be a harmonic of a solid-state laser (for example, a third harmonic of a YAG laser (wavelength: 355 nm), etc.).

The conversion unit 13 is a vacuum ultraviolet laser oscillation unit that converts the ultraviolet laser UV guided by the light guide lens 11 into a vacuum ultraviolet laser. The conversion unit 13 is, for example, a gas cell filled with a rare gas such as xenon, argon, or krypton. The rare gas absorbs and resonates a plurality of photons of the ultraviolet laser UV guided by the light guide lens 11 mainly at the convergence point of the ultraviolet laser UV in the converter 13, and oscillates a vacuum ultraviolet laser VUV. The wavelength of such a vacuum ultraviolet laser VUV is, for example, 118 nm when it is derived from xenon. However, not all photons of the ultraviolet laser UV are used to oscillate the vacuum ultraviolet laser VUV, and a part of the ultraviolet laser UV is emitted to the outside through the condenser lens 15 together with the vacuum ultraviolet laser VUV. . Note that the rare gas is sealed from the rare gas inlet 131.

The condensing lens 15 condenses the vacuum ultraviolet laser VUV oscillated in the conversion section 13 so as to converge it within the ionization section 23 of the ion generation section 20 . Further, since the vacuum ultraviolet laser VUV and the ultraviolet laser UV have different wavelengths, the refraction angles at the condenser lens 15 are also different. Therefore, the condensing lens 15 separates the vacuum ultraviolet laser VUV and the ultraviolet laser UV by utilizing the difference in refraction angle between the vacuum ultraviolet laser VUV and the ultraviolet laser UV. The condenser lens 15 is made of, for example, magnesium fluoride, lithium fluoride, or the like.

Further, the vacuum ultraviolet ray generating section 10 described above is arranged so that the vacuum ultraviolet laser VUV to be generated advances to the ionization section 23, which will be described later, in parallel with the x-axis in the figure. In this case, the target ions IS generated in the ionization unit 23 tend to have a lower degree of convergence in the x-axis direction than in the z-axis direction.

Of the target ions IS generated when the sample S spread in the ion generation region 236 is irradiated with a vacuum ultraviolet laser, a plane (y-z The target ions IS existing within the surface) are taken into the orbit most efficiently. The efficiency with which the target ion IS converges on the orbit decreases as it moves away from the orbital plane (yz plane). In other words, by irradiating the vacuum ultraviolet laser VUV in the x-axis direction, the effective interaction volume between the target ion IS and the vacuum ultraviolet laser VUV can be maximized. In this way, by aligning the direction axis in which the target ion IS is difficult to converge with the direction axis in which the degree of permissible convergence of the target ion IS in the multi-orbit time-of-flight mass spectrometer 30 is high, the detection sensitivity of the target ion IS can be increased. improves.

The ion generator 20 ionizes the sample S by one photon using a vacuum ultraviolet laser VUV to generate target ions IS. The ion generating section 20 has a vacuum chamber 21 , an ionizing section 23 , a first aperture 25 , a second aperture 27 , and an electron gun 29 .

The vacuum chamber 21 includes a space 211, houses each part of the ion generating section 20, and maintains a vacuum (reduced pressure) state within the space 211. Further, the vacuum chamber 21 has a view port 215.

The vacuum ultraviolet laser VUV oscillated in the vacuum ultraviolet generator 10 is introduced into the ion generator 20 via the condenser lens 15 . The vacuum ultraviolet laser VUV needs to be propagated in vacuum after passing through the condensing lens 15, and the condensing lens 15 is directly attached to the side surface of the vacuum chamber 21. Note that, without being limited to the illustrated embodiment, the conversion section 13 and the vacuum chamber 21 may be connected by a lens barrel whose interior is evacuated or replaced with an inert gas.

The viewport 215 is a translucent window member provided on the optical path of the ultraviolet laser UV reflected by a second aperture 27, which will be described later. From the view port 215, it is possible to confirm the irradiation position of the ultraviolet laser UV within the ion generating section 20, particularly the irradiation position on the second aperture 27, which will be described later. Thereby, it becomes possible to estimate the optical axis of the vacuum ultraviolet laser VUV, which cannot be visually recognized, and it becomes possible to adjust the optical axis of the vacuum ultraviolet laser VUV.
The viewport 215 is made of a material that is resistant to ultraviolet laser UV, such as synthetic quartz.

The ionization section 23 irradiates the sample S with a vacuum ultraviolet laser VUV, and pushes out one-photon ionized target ions IS to the multi-turn time-of-flight mass spectrometry section 30 . As shown in FIG. 2, the ionization section 23 includes an extrusion electrode 231, an extraction electrode 232, and an extraction electrode 233. The push-out electrode 231, the pull-out electrode 232, and the pull-in electrode 233 are arranged in this order along the planned traveling direction of the target ions IS. Voltages of different magnitudes can be applied to these push electrode 231, extraction electrode 232, and pull-in electrode 233, respectively. Based on the potential difference generated between these electrodes 231 to 233, the target ion IS is accelerated by two stages of acceleration. It is pushed out to the multi-turn time-of-flight mass spectrometry section 30.

The push-out electrode 231 has a cup shape and is arranged such that its opening faces the pull-out electrode 232. The extrusion electrode 231 also has a hole 234 on its side surface for passing the vacuum ultraviolet laser VUV and introducing it into the extrusion electrode 231, and a hole 234 for introducing the sample S from the introduction section 40, which will be described later, into the extrusion electrode 231. A hole 235 and a hole 239 for introducing the electron beam EB from the electron gun 29 into the pushing electrode 231 are provided.

Then, in the ion generation region 236 of the space formed by the push-out electrode 231 and the extraction electrode 232 described later, the vacuum ultraviolet laser VUV or the electron beam EB collides with the sample S, and the sample S is ionized. Target ions IS are generated.

Each molecule in the sample S has its own ionization potential. Then, by bombarding the molecules with photons having photon energy exceeding this ionization potential, the molecules are ionized with one photon. Such ionization of a molecule by one photon does not cause cleavage of the target molecule. In addition, all molecules whose ionization potential is less than the photon energy can be ionized by the vacuum ultraviolet laser VUV, and it is also possible to ionize multiple types of target substances at the same time. That is, one-photon ionization enables analysis of multiple types of target substances. In this embodiment, in order to perform such one-photon ionization of the target substance in the sample S, a vacuum ultraviolet laser VUV can be used.

Further, the bottom of the push-out electrode 231 has a shape having a depression curved in a direction opposite to the traveling direction of the target ions IS. Since the bottom of the extrusion electrode 231 has such a curved surface shape, an appropriate potential distribution can be formed, and temporal isometricity can be achieved in each acceleration path for the target ion IS located on the curved equipotential surface. can be given. As a result, the target ions IS can be pushed out toward the extraction electrode 232 while converging. This improves the extraction efficiency of target ions IS. As a result, the peak width of the target ion IS detected by the detector 39, which will be described later, becomes narrower and the peak intensity improves, and all of detection sensitivity, resolution, and quantitative performance are improved.

In addition, in order to satisfy the temporal isometricity until the target ions IS generated at various positions in the ion generation region 236 are extracted and to spatially converge the target ions IS, it is necessary to preferably has a shape that has a lens effect and forms a potential distribution whose focus point can be adjusted at the position of the extraction electrode 232. Further, the bottom of the push-out electrode 231 is preferably curved so that equipotential lines having concentric curves centered on a predetermined position of the push-out electrode 231 can be formed.

The extraction electrode 232 is arranged between the extrusion electrode 231 and the extraction electrode 233. The extraction electrode 232 is formed in a mesh shape and is configured to allow the target ions IS to pass therethrough. Then, based on the potential difference between the extraction electrode 232 and the pushing electrode 231, the target ions IS are extracted from the ion generation region 236, passing through the extraction electrode 232, and toward the drawing electrode 233 side.

Further, the extraction electrode 232 has a shape in which an ion passage portion 237 centered near the passage position of the target ions IS has a depression curved in a direction opposite to the traveling direction of the target ions IS. By providing the extraction electrode 232 with the ion passing portion 237 having such a curved surface shape, it is possible to form an appropriate potential distribution similarly to the push-out electrode 231, and for the target ions IS on the curved equipotential surface, It is possible to provide temporal isometricity in each acceleration path. As a result, as described above, detection sensitivity, resolution, and quantitative performance are all improved.

The extraction electrode 233 is arranged downstream of the path of the target ions IS than the extraction electrode. The extraction electrode 233 accelerates the target ions IS that have passed through the extraction electrode 232 based on the potential difference generated between the extraction electrode 232 and the extraction electrode 233, and draws them into the multi-turn time-of-flight mass spectrometer 30 through the hole 238.

Further, the ionization unit 23 has an electrostatic lens (not shown) as necessary, and the electrostatic lens spatially further converges the target ions IS that have passed through.

The ionization unit 23 as described above has excellent extraction efficiency of the target ions IS, is advantageous in convergence of the target ions IS, and can improve all of sensitivity, resolution, and quantitative performance. On the other hand, the space for introducing the vacuum ultraviolet laser VUV through the hole 234 becomes small. In this case, the ionization section 23 may be damaged by the ultraviolet laser UV that enters together with the vacuum ultraviolet laser VUV. In particular, when the vicinity of the hole 234 of the extrusion electrode 231 is irradiated with ultraviolet laser UV, the extrusion electrode 231 becomes electrically charged, reducing the extraction efficiency of the target ions IS in the ionization section 23, or damaging the extrusion electrode 231, causing ionization. The portion 23 may be damaged.

However, in the vacuum ultraviolet one-photon ionization mass spectrometer 1 according to the present embodiment, by including the first aperture 25 and the second aperture 27, the ultraviolet laser UV can be efficiently blocked and the above problems can be solved. is prevented.

As shown in FIG. 1, the first aperture 25 is arranged between the ionization section 23 and the condenser lens 15 and along the optical axis of the vacuum ultraviolet laser VUV. The first aperture 25 has a hole 251 on the optical axis of the vacuum ultraviolet laser VUV, and allows the vacuum ultraviolet laser VUV to pass through the hole 251. On the other hand, as described above, the optical path of the ultraviolet laser UV is separated into the vacuum ultraviolet laser VUV and the ultraviolet laser UV by the condenser lens 15. Therefore, most of the ultraviolet laser UV is irradiated onto the portion other than the hole 251 of the first aperture 25 and is blocked.

Here, the present inventors realized that the ultraviolet laser UV cannot be sufficiently blocked by the ionization section 23 only by the first aperture 25. That is, when increasing the intensity of the vacuum ultraviolet laser VUV, the irradiation intensity of the ultraviolet laser UV also naturally increases. In this case, when most of the ultraviolet laser UV is emitted from the condenser lens 15, it is converged and irradiated onto the first aperture 25, where it is blocked. On the other hand, a part of the ultraviolet laser UV does not travel along the same optical path as other ultraviolet lasers UV due to diffusion or the like, and is not necessarily blocked by the first aperture 25. Then, a part of the ultraviolet laser UV can pass through the hole 251 of the first aperture 25 and proceed toward the ionization section 23 side. Alternatively, when adjusting the optical axis of the vacuum ultraviolet laser VUV, a part of the ultraviolet laser UV may pass through the first aperture 25 and be irradiated onto the ionization section 23. However, in this embodiment, the second aperture 27 can also block such ultraviolet laser UV.

That is, the optical path length between the condenser lens 15 and the second aperture 27 after exiting the condenser lens 15 is longer than the optical path length between the condenser lens 15 and the first aperture 25, and , the gap between the spot positions of the vacuum ultraviolet laser VUV and the ultraviolet laser VU becomes larger, and the ultraviolet laser UV that has passed through the first aperture 25 is also blocked by the second aperture 27. The optical path length between the condensing lens 15 and the second aperture 27 is preferably at least twice the optical path length between the condensing lens 15 and the first aperture 25, more preferably at least 3 times the optical path length between the condensing lens 15 and the first aperture 25. It is less than twice that.

As shown in FIGS. 1 and 2, the second aperture 27 is arranged between the ionization section 23 and the first aperture 25 and along the optical axis of the vacuum ultraviolet laser VUV. More specifically, the second aperture 27 is arranged adjacent to the ionization section 23. The second aperture 27 has a hole 271 on the optical axis of the vacuum ultraviolet laser VUV, and allows the vacuum ultraviolet laser VUV to pass through the hole 271.

On the other hand, the second aperture 27 blocks the ultraviolet laser UV on a surface 273 facing the first aperture 25. Specifically, the second aperture 27 absorbs or reflects the ultraviolet laser UV at the surface 273. Thereby, it is possible to prevent the ultraviolet laser UV from reaching the ionization section 23.

The second aperture 27 may be made of any material, but is preferably made of a conductive material such as a metal material, a conductive ceramic material, or a carbon material. In this case, the second aperture is preferably grounded as shown in FIG. This makes it possible to remove charges generated by irradiation with the ultraviolet laser UV and prevent charging. As a result, it is possible to prevent the ionization section 23 from being affected by the charging of the second aperture 27. Note that examples of the metal material include iron, SUS, aluminum, and the like.

Further, the surface 273 of the second aperture 27 is an inclined surface inclined with respect to the optical axis of the vacuum ultraviolet laser VUV. Thereby, if the surface 273 of the second aperture 27 is made of a reflective material, in particular a metallic material, the ultraviolet laser UV can be reflected at the surface 273, for example into the aforementioned view port 215. Specifically, the surface 273 can have a minimum angle α of, for example, 30° or more and 60° or less with respect to the optical axis of the vacuum ultraviolet laser VUV.

The electron gun 29 shown in FIGS. 1 and 3 is arranged below the ionization section 23. The electron gun 29 is operated in a direction different from the direction in which the vacuum ultraviolet laser VUV from the vacuum ultraviolet generator 10 enters the ionization section 23, in this embodiment, in a direction perpendicular to the direction in which the vacuum ultraviolet laser VUV enters the ionization section 23 ( The electron beam EB is emitted in a direction (parallel to the z-axis).

By causing such an electron beam EB to collide with the sample S in the ion generation region 236 of the ionization section 23, the sample S can be ionized and target ions IS can be generated. That is, in this embodiment, the target ion IS is generated by selectively using a vacuum ultraviolet one-photon ionization method using a vacuum ultraviolet laser VUV and a so-called electron ionization method using an electron beam EB. is possible.

The multi-orbit time-of-flight mass spectrometer 30 detects the target ion IS and measures the mass of the target ion IS. As shown in FIG. 3, the multi-turn time-of-flight mass spectrometer 30 includes an entrance electrode 31, a plurality of orbital electrodes 33, an ion gate 35, an exit electrode 37, and a detector 39.

The input electrode 31 is capable of forming a predetermined electric field, and causes the target ions IS extracted in the ion generation section 20 to enter the orbit in the multi-turn time-of-flight mass spectrometry section 30 . A constant voltage is applied to the plurality of orbiting electrodes 33, which guide the target ions IS that have entered the orbit and cause them to orbit around the orbit. In addition, in this embodiment, the four curved orbiting electrodes 33 are arranged so that the orbit depicts a figure eight.

The ion gate 35 is applied periodically to remove ions having a mass-to-charge ratio outside the desired range. Further, the ion gate 35 also removes ions that are delayed in their orbit from among the target ions IS orbiting in the orbit.

The output electrode 37 is applied with an electric field to form an electric field, thereby guiding the target ions IS that have made several orbits and outputting them to the detector 39 .

The detector 39 is, for example, a daily ion detector, and detects the target ions IS that have reached the detector 39.

The introduction section 40 is connected to the ion generation section 20 and introduces the sample S into the space 211 of the ion generation section 20 . Specifically, the sample S is continuously injected from the introduction section 40 into the reduced pressure ion generation section 20 . The injected sample S reaches the ion generation region 236 of the ionization section 23, where it is irradiated with a vacuum ultraviolet laser VUV or an electron beam EB.

As shown in FIG. 1, the ultraviolet detection unit 50 is arranged on the optical path of the ultraviolet laser UV reflected by the surface 273 of the second aperture 27. The ultraviolet light detection unit 50 is, for example, a photodiode, and detects the ultraviolet laser UV reflected from the surface 273 of the second aperture 27. In this manner, by detecting the intensity and position of the reflected ultraviolet laser UV in the ultraviolet detection unit 50, it becomes possible to estimate the intensity and the position of the optical axis of the vacuum ultraviolet laser VUV. As a result, the light intensity and/or optical axis of the vacuum ultraviolet laser VUV can be adjusted based on the intensity and position of the ultraviolet laser UV detected by the ultraviolet detector 50.

Therefore, the vacuum ultraviolet one-photon ionization mass spectrometer 1 has an adjustment mechanism that adjusts the optical axis and/or light intensity of the vacuum ultraviolet laser VUV according to the position and/or intensity of the ultraviolet laser UV detected by the ultraviolet detection unit 50. (not shown). This adjustment mechanism enables more accurate control of the optical axis and/or light amount of the vacuum ultraviolet laser VUV.

Although not shown, the vacuum ultraviolet one-photon ionization mass spectrometer 1 is provided with a control device for controlling the operation of the vacuum ultraviolet one-photon ionization mass spectrometer 1. The control device can control the operations of each component of the vacuum ultraviolet one-photon ionization mass spectrometer 1 described above. The control device may be a processor such as a CPU (Central Processing Unit), or a control board on which a processor and a storage element such as a memory are mounted. Alternatively, the control device may be a general-purpose information processing device such as a PC (Personal Computer). The various functions described above can be realized and executed by the processor of the control unit executing arithmetic processing according to a predetermined program.
The vacuum ultraviolet one-photon ionization mass spectrometer 1 according to the present embodiment has been described above.

<2. Operation of vacuum ultraviolet one-photon ionization mass spectrometer>
Next, the operation of the vacuum ultraviolet one-photon ionization mass spectrometer according to the present embodiment will be described using the operation of the vacuum ultraviolet one-photon ionization mass spectrometer 1 as an example.

(2.1. Vacuum ultraviolet one-photon ionization mass spectrometry)
The operation of the vacuum ultraviolet one-photon ionization mass spectrometer 1 when performing vacuum ultraviolet one-photon ionization mass spectrometry will be described.
In this case, first, the sample S is continuously injected into the ion generating section 20 from the introduction section 40. The injected sample S reaches the ion generation region 236 of the ionization section 23, where it is irradiated with a vacuum ultraviolet laser VUV.

Note that the sample S is not particularly limited as long as it can be soft ionized by vacuum ultraviolet laser VUV, and various gaseous compositions and compounds can be used. Sample S includes, for example, low-molecular or high-molecular organic compounds such as aromatic compounds and hydrocarbons, exhaust gases emitted from industrial facilities such as factories, gas turbines, and incinerators, and transportation machines such as automobiles and airplanes. can be. Note that the number of compounds detected and quantified by the vacuum ultraviolet one-photon ionization mass spectrometer 1 may be one or more than one.

On the other hand, the vacuum ultraviolet laser VUV is oscillated in the vacuum ultraviolet generator 10. Specifically, first, pulsed ultraviolet laser UV of a solid-state laser oscillated by a solid-state laser oscillation unit (not shown) is introduced into the conversion unit 13 via the light guide lens 11 . Next, the ultraviolet laser UV introduced into the converting section 13 excites and resonates a rare gas such as xenon sealed in the converting section 13 at its convergence point to oscillate a vacuum ultraviolet laser VUV.

The vacuum ultraviolet laser VUV oscillated in the conversion section 13 is condensed by the condenser lens 15 so as to be converged within the ionization section 23 of the ion generation section 20 . The focused vacuum ultraviolet laser VUV passes through the hole 251 of the first aperture 25 and the hole 271 of the second aperture 27 and reaches the ion generation region 263 of the ionization section 23 .

Here, the ultraviolet laser UV not used for conversion of the vacuum ultraviolet laser VUV is condensed by the condenser lens 15 in the same way as the vacuum ultraviolet laser VUV. However, the vacuum ultraviolet laser VUV and the ultraviolet laser UV can be separated by utilizing the difference in refraction angle between the vacuum ultraviolet laser VUV and the ultraviolet laser UV. Most of the ultraviolet laser UV emitted from the condensing lens 15 is blocked in a portion of the first aperture 25 other than the hole 251. Further, the ultraviolet laser UV having a slight intensity that has passed through the first aperture 25 is further blocked at the surface 273 of the second aperture 27 . In this way, the ionization section 23 is prevented from reaching the ionization section 23 of the intense ultraviolet laser UV that would affect the analysis or damage the device, while the vacuum ultraviolet laser VUV is efficiently directed to the ionization section 23 of the ion generation section 20. The ion generation region 236 is reached.

In the ion generation region 236 of the ionization unit 23, the vacuum ultraviolet laser VUV ionizes the sample S by one photon, and target ions IS are generated. The target ions IS are temporally and spatially converged and accelerated by applying an appropriate potential difference to the extrusion electrode 231, the extraction electrode 232, and the extraction electrode 233, and are extruded to the multi-turn time-of-flight mass spectrometer 30. It can be done.

In the multi-turn time-of-flight mass spectrometer 30, the target ion IS is first guided into an orbit by the entrance electrode 31 to which a predetermined voltage is applied. Then, the target ion IS orbits the intended number of times by the four orbiting electrodes 33 to which a constant voltage is applied. In this process, the application to the input electrode 31 is terminated by the time the first round is completed. Further, the ion gate 35 is periodically applied to remove ions having a mass-to-static charge ratio in a range other than the intended range.

After the target ions IS have orbited the intended number of times, the output electrode 37 is applied to form an electric field to guide the target ions IS and output them to the detector 39 . Then, the detector 39 detects the target ion IS that has arrived. Then, the m/z value is determined from the relationship between the oscillation time of the vacuum ultraviolet laser VUV and the subsequent flight time until it reaches the detector 39. Further, the signal intensity for each m/z value is detected according to the amount of target ions IS detected by the detector 39.

The information obtained in this way allows identification and quantification of the mass number of the target ion IS. That is, the mass number of the target ion IS is specified by the m/z value. Furthermore, a calibration curve between the concentration of the sample S and the signal intensity of the corresponding m/z value is created in advance, and the concentration of the sample S is calculated by substituting the detected signal intensity into the calibration curve. Such identification and quantification of the mass number of the sample S can be performed by a control device (not shown).

As described above, the mass and concentration of the sample S are specified. The vacuum ultraviolet one-photon ionization mass spectrometry described above combines vacuum ultraviolet one-photon ionization, which allows soft ionization, and multi-turn time-of-flight mass spectrometry, which has high mass resolution, to achieve mass spectrometry with extremely high accuracy. It also becomes possible to identify and quantify sample S. For example, by employing a device equivalent to the vacuum ultraviolet one-photon ionization mass spectrometer 1 described above, the present inventors were able to analyze cyclohexane (C ₆ H ₁₂ , mass number 84.0939), which has the same integer mass number. , and thiophene (C ₄ H ₄ S, mass number 84.0034), and confirmed that they can be separated and detected fragment-free. That is, it was possible to detect and quantify these molecules as separate peaks.

Such a combination of vacuum ultraviolet one-photon ionization method and multi-turn time-of-flight mass spectrometry employs the first aperture 25 and the second aperture 27, that is, employs a plurality of apertures, This was made possible for the first time by efficiently blocking ultraviolet laser UV.

Furthermore, before or after vacuum ultraviolet one-photon ionization mass spectrometry, information about the position and/or intensity of the ultraviolet laser is obtained from the viewport 215 and/or the ultraviolet detection unit 50 as necessary. Based on this information, the optical axis and light intensity of the vacuum ultraviolet laser VUV are adjusted as appropriate.
The vacuum ultraviolet one-photon ionization mass spectrometry using the vacuum ultraviolet one-photon ionization mass spectrometer 1 has been described above.

(2.2. Electron ionization mass spectrometry)
Next, the operation of the vacuum ultraviolet one-photon ionization mass spectrometer 1 when performing electron ionization mass spectrometry will be described. In electron ionization mass spectrometry, unlike vacuum ultraviolet one-photon ionization mass spectrometry, instead of using the vacuum ultraviolet laser VUV from the vacuum ultraviolet generator 10, the electron beam EB from the electron gun 29 is used to ionize the sample S. The main difference is that it is used for Therefore, this point will be mainly explained, and the explanation of similar matters will be omitted.

That is, first, the sample S is continuously injected into the ion generating section 20 from the introduction section 40 . The injected sample S reaches the ion generation region 236 of the ionization section 23.

On the other hand, the electron gun 29 irradiates the ion generation region 236 of the ionization unit 23 with the electron beam EB, and the sample S is ionized by the electron beam EB to generate target ions IS. The subsequent analysis of the generated target ions IS is the same as in the vacuum ultraviolet one-photon ionization mass spectrometry described above.

As described above, by including the electron gun 29, the vacuum ultraviolet one-photon ionization mass spectrometer 1 can perform electron ionization mass spectrometry instead of vacuum ultraviolet one-photon ionization mass spectrometry. With the electron ionization method, it is possible to measure low molecules such as CO and CO ₂ without causing fragmentation problems. Further, since the electron ionization method has a rich database of fragmented ions, it is suitable for conveniently analyzing a sample S whose composition is unknown. Although the vacuum ultraviolet one-photon ionization method does not have a comprehensive database of fragmented ions compared to the electron ionization method, it enables more precise mass spectrometry and quantification using soft ionization. Therefore, using the vacuum ultraviolet one-photon ionization mass spectrometer 1, it is possible to select a mass spectrometry method according to the situation.

The operation of the vacuum ultraviolet one-photon ionization mass spectrometer according to this embodiment has been described above.

Although preferred embodiments of the present invention have been described above in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea stated in the claims. It is understood that these also naturally fall within the technical scope of the present invention.

For example, in the embodiment described above, the second aperture 27 is described as having the surface 273 inclined with respect to the optical axis of the vacuum ultraviolet laser VUV, but the present invention is not limited to this, and the second aperture 27 is , the surface on the incident side of the vacuum ultraviolet laser may have any angle and shape.

Further, the second aperture only needs to be able to block the ultraviolet laser, and does not need to absorb or reflect the ultraviolet laser. Furthermore, in this case, the view port and the ultraviolet detection section disposed in the ion generation section may be omitted.

For example, in the embodiment described above, the vacuum ultraviolet one-photon ionization mass spectrometer 1 was described as having the electron gun 29, but the present invention is not limited to this, and the vacuum ultraviolet one-photon ionization mass spectrometer includes an electron gun. You don't have to be prepared.

Furthermore, for example, the ionization section used in the present invention does not need to have the structure of the electrode in this embodiment described above, and may employ a known structure. For example, the ionization section does not need to include an extraction electrode. Moreover, the extrusion electrode and the extraction electrode do not need to be curved.

Further, in the present invention, various known multi-turn time-of-flight mass spectrometers having configurations other than the multi-turn time-of-flight mass spectrometer 30 in the above-described embodiment may be employed. For example, the orbit of the ions in the multi-turn time-of-flight mass spectrometer is not limited to the figure-eight shape described above, and can be appropriately selected from, for example, a circular orbit, a spiral orbit, or the like. Furthermore, in this case, the configurations of the various electrodes arranged in the multi-turn time-of-flight mass spectrometer are also changed.

1 Vacuum ultraviolet one-photon ionization mass spectrometer 10 Vacuum ultraviolet ray generation section 11 Light guide lens 13 Conversion section 131 Rare gas inlet 15 Condensing lens 20 Ion generation section 21 Vacuum chamber 211 Space 215 View port 23 Ionization section 231 Extrusion electrode 232 Extraction Electrode 233 Pull-in electrode 234, 235, 238, 239 Hole 236 Ion generation region 237 Ion passage section 25 First aperture 251 Hole 27 Second aperture 271 Hole 273 Surface 29 Electron gun 30 Multi-turn time-of-flight mass spectrometry section 31 Injection Electrode 33 Circulating electrode 35 Ion gate 37 Output electrode 39 Detector 40 Introduction part 50 Ultraviolet detection part

Claims (9)

A vacuum ultraviolet ray generator that generates a vacuum ultraviolet laser;
an ion generation unit that one-photonizes the sample with the vacuum ultraviolet laser to generate target ions;
a multi-orbit time-of-flight mass spectrometer that detects the target ions and measures the mass of the target ions,
The vacuum ultraviolet ray generation section includes a conversion section that converts the ultraviolet laser into the vacuum ultraviolet laser, and a condensing lens that focuses the vacuum ultraviolet laser and introduces it into the ion generation section,
The ion generating section is
an ionization unit that irradiates the sample with the vacuum ultraviolet laser and pushes out the one-photon ionized target ions to the multi-turn time-of-flight mass spectrometry unit;
a first aperture disposed between the ionization section and the condensing lens and along the optical axis of the vacuum ultraviolet laser;
A vacuum ultraviolet one-photon ionization mass spectrometer, comprising a second aperture disposed between the ionization section and the first aperture and along the optical axis of the vacuum ultraviolet laser. The vacuum ultraviolet one-photon ionization mass spectrometer according to claim 1, wherein the second aperture is arranged adjacent to the ionization section. The vacuum ultraviolet one-photon ionization mass spectrometer according to claim 1 or 2, wherein the second aperture is grounded. The vacuum ultraviolet laser according to any one of claims 1 to 3, wherein the second aperture has a surface facing the first aperture that is inclined with respect to the optical axis of the vacuum ultraviolet laser. One-photon ionization mass spectrometer. 5. The vacuum ultraviolet one-photon ionization mass spectrometer according to claim 4, wherein the ion generating section includes a view port through which the ultraviolet laser reflected by the inclined surface can pass. The vacuum ultraviolet one-photon ionization mass spectrometer according to claim 4 or 5, further comprising an ultraviolet detection section that detects the ultraviolet laser reflected by the inclined surface of the second aperture. The vacuum ultraviolet one-photon according to claim 6, further comprising an adjustment mechanism that adjusts the optical axis and/or light intensity of the vacuum ultraviolet laser according to the position and/or intensity of the ultraviolet laser detected by the ultraviolet detection unit. Ionization mass spectrometer. The vacuum ultraviolet one photon according to any one of claims 1 to 7, wherein the optical axis of the vacuum ultraviolet laser is perpendicular to a plane formed by the orbit of the target ion in the multi-turn time-of-flight mass spectrometer. Ionization mass spectrometer. The vacuum ultraviolet 1 according to any one of claims 1 to 8, wherein the ionization unit further includes an electron gun capable of irradiating the sample with an electron beam perpendicular to the optical axis of the vacuum ultraviolet laser. Photon ionization mass spectrometer.

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