EP1220285A2 - Ion source in which a UV/VUV light source is used for ionization - Google Patents

Abstract

The invention relates to an ion source in which the ions have been ionized by UV / VUV light and the use thereof. The object of the invention is to provide an ion source with a light source of high useful photon density and to indicate an advantageous use. This task is solved by the fact that the light source consists either of a deuterium tape, a hollow micro cathode lamp, a micro tip lamp, a direct current discharge lamp, a barrier discharge lamp or an electron beam operated UV / VUV lamp with the following components, an electron gun, a membrane, which separates the space of the electron gun against a gas space shoots and through which the electron beam passes, a noble gas or a noble gas-containing gas mixture in the gas space, the electron beam passing through the membrane generating light in the gas space and optical components for imaging the light emission volume in the ionization space.

Description

The invention relates to an ion source in the UV / VUV light is used for ionization, according to the generic term of Claim 1, and their use.

VUV light can be generated by so-called micro hollow cathode lamps become. One or more burning at the same time Discharges in small (typically 100 µm diameter) openings in constricted in a dielectric. Because gas discharge parameters with can scale the product of diameter and gas pressure with the arrangement in turn, because of the small diameter with high Gas pressure maintain a stable glow discharge and VUV excimer light is generated in the dense gas [1].

Another alternative variant for generating brilliant UV / VUV radiation is a discharge in dense noble gases between pointed metal electrodes or a pointed metal electrode and a metal surface. These varinates of the corona discharge are operated with both high frequency and direct voltage [D. E. Murnick, M. Salvermoser, private communication, Gaseous Electronics Conference "GEC" 2000, 24.-27. October, Houston, Texas, USA, accepted for publication].

A particularly suitable for ion sources UV / VUV light source is the electron beam pumped structure described below.
Vacuum ultraviolet light generation in the light source, which generates the ions in the ion source by photoionization, is carried out by exciting a dense gas with an electron beam [2, 3]. The gas usually consists of one of the noble gases He, Ne, Ar, Kr or Xe or a noble gas and the admixture of another gas, such as hydrogen.

State of the art

Mass spectrometry with laser-based VUV single-photon ionization the VUV light from UV laser pulses by frequency tripling is generated in a gas cell, and their use chemical analysis is described in the literature [5-8]. However, the laser-based generation of VUV shows light some serious disadvantages.

The VUV generation process in a gas cell is very inefficient. Therefore, powerful and therefore very expensive, large solid-state lasers are used (mostly Nd: YAG lasers with 355 nm). In operation, high additional costs arise from flash lamps (needed to pump the laser medium) and maintenance. Farther can generally only be a single one with a solid-state laser VUV wavelength can be generated (118 nm when using 355 nm laser radiation). Tunable solid-state lasers are extreme complex and cannot be used for practical analytical tasks. Frequency tripling is a very sensitive one nonlinear process, its VUV yield with the third power the primary radiation is scaled. This leads to a high one System instability and fluctuations in VUV yield. Furthermore, there is a complex separation of the primary radiation 355 nm necessary for fragmentation by VUV absorption to prevent ions formed.

In addition to the laser-based VUV single-photon ionization is in principle also the use of conventional low pressure emission lamps (e.g. mercury vapor lamp) for ion generation for mass spectrometry possible.

Deuterium lamps based on a gas discharge in a deuterium gas can also be used and if they have a window that is transparent to vacuum ultraviolet light, e.g. B consisting of MgF ₂ or LiF, emit continuum radiation and the so-called Lyman and Werner molecular bands around 160 and 130 nm, respectively. Deuterium lamps are commercially available from various manufacturers.

Furthermore, VUV can light with so-called dielectrically disabled Discharges are generated, with a gas discharge at least one of the electrodes with a non-conductive layer is provided. [9]. With this arrangement, for example, in dense, cold noble gases by applying a medium frequency AC voltage to the electrodes excimer light in the VUV range be generated.

However, these lamps produce a wide range of wavelengths (requires wavelength separation and requires a low one Usable photon density) and are not very brilliant (for example poor focusability).

Task and examples

The object of the invention is an ion source with a light source to provide high useful photon density as well indicate an advantageous use

This object is achieved by the features of the claims 1 and 7. The subclaims describe advantageous refinements the invention.

Figur 1

Ionisationsraum eines Flugzeitmassenspektrometers mit elektronenstrahlgepumpter Excimer VUV-Lampe.

Figur 2

Detaildarstellung eines Teils der Excimer-VUV-Lampe mit einem Parabolspiegel zur Zusammenfassung des UV/VUV-Lichtes.

Figur 3

Übersichtsdarstellung des Flugzeitmassenspektrometers (TOFMS) mit Excimer-VUV-Lampen-Ionisation.

Figur 4

Optische Aufbauten zur Einkopplung des UV/VUV-Lichtes in die Ionisationsregion des Flugzeitmassenspektrometers (TOFMS).

Figur 5

Gemessene Zeitabläufe während eines Nachweiszyklus mit einem Excimer-VUV-Lampen-Ionisations Flugzeitmassenspektrometer (Prototyp). Dargestellt sind der VUV-Lichtimpuls (Kr), Abzugspannungsimpuls und das Ionendetektorsignal.

Figur 6

Wellenlängenselektivität der Massenspektrometrie mit Excimer-VUV-Lampen-Ionisation. Dargestellt ist das Wellenlängenspektrum der Argon bzw. Krypton Excimer-Emission sowie die korrespondierenden Excimer-VUV-Lampen-Ionisation Flugzeitmassenspektren einer Mischung aus Benzol und Toluol.

Figur 7

Mit einem Excimer-VUV-Lampen-Ionisations Flugzeitmassenspektrometer (Prototyp) durchgeführte on-line Messung von Abgas eines Motorrads während der Startphase (Excimergas: Argon)

Figur 8

Schematische Übersichtsdarstellung des Quadrupol-Massenspektrometers (QMS) mit Excimer-VUV-Lampen-Ionisation.

Figur 9

Schematische Übersichtsdarstellung eines Detektors für Gase auf Basis einer Ionisationskammer mit Excimer-VUV-Lampen-Ionisation und Detektion der erzeugten Ladungen.

Figur 10

Schematische Übersichtsdarstellung einer VUV-Lampe, bei der durch Ablenkung des Elektronenstrahls auf verschiedene Eximer-VUV-Lichtquellen mit unterschiedlicher Gasfüllung die Wellenlänge des emittierten Lichts verändert werden kann.

The invention is explained in more detail below on the basis of exemplary embodiments and the figures. Show:

Figure 1

Ionization space of a time-of-flight mass spectrometer with electron beam pumped Excimer VUV lamp.

Figure 2

Detail of part of the Excimer VUV lamp with a parabolic mirror to summarize the UV / VUV light.

Figure 3

Overview of the time-of-flight mass spectrometer (TOFMS) with excimer VUV lamp ionization.

Figure 4

Optical assemblies for coupling the UV / VUV light into the ionization region of the time-of-flight mass spectrometer (TOFMS).

Figure 5

Measured timings during a detection cycle with an excimer VUV lamp ionization time-of-flight mass spectrometer (prototype). The VUV light pulse (Kr), withdrawal voltage pulse and the ion detector signal are shown.

Figure 6

Wavelength selectivity of mass spectrometry with excimer VUV lamp ionization. The wavelength spectrum of the argon or krypton excimer emission is shown as well as the corresponding excimer VUV lamp ionization time-of-flight mass spectra of a mixture of benzene and toluene.

Figure 7

On-line measurement of exhaust gas from a motorcycle during the start-up phase (excimer gas: argon) carried out with an excimer VUV lamp ionization time-of-flight mass spectrometer (prototype)

Figure 8

Schematic overview of the quadrupole mass spectrometer (QMS) with excimer VUV lamp ionization.

Figure 9

Schematic overview of a detector for gases based on an ionization chamber with excimer VUV lamp ionization and detection of the generated charges.

Figure 10

Schematic overview of a VUV lamp, in which the wavelength of the emitted light can be changed by deflecting the electron beam onto various Eximer VUV light sources with different gas fillings.

1) Time-of-flight mass spectrometer with electron beam pumped UV / VUV excimer lamp

FIG. 1 shows an example of the configuration of the ionization region of a time-of-flight mass spectrometer with VUV Eximer lamp ionization. FIG. 2 shows a section of the beam coupling and FIG. 3 shows the entire mass spectrometer with the VUV Eximerlampe. Figure 4 shows different options for coupling the UV / VUV light into the ionization chamber 14 or to the ionization site 23. FIGS. 5 and 6 show examples Application results with the developed prototype.

The VUV Eximer lamp unit is e.g. via a flange to the Ionization chamber 14 coupled. The upper part of the lamp serves for generating an electron beam 8 with the electron gun 1 and has a vacuum. The electron tube 2 is about a getter pump 4 or a pump nozzle 5 is evacuated. The Electron beam 8 is focused on the film 3. The foil e.g. made of ceramic silicon nitride and separates that High vacuum of the electron tube 2 from the gas space 9. In the gas room 9 there is a gas mixture that is pumped over the electron beam Excimer process in the UV / VUV spectral range lights up (radiative Decay of the excimers). The gas space 9 is a Getter 10 cleaned. There is a suitable one in the gas space 9 coated parabolic mirror 11, which in the luminescent volume 13 formed UV / VUV light combined into a parallel beam and throws it on the lens 12. This structure enables a good use of the 360 degree radiation solid angle. A reflective coating of those facing gas space 9 Side of slide 3 can be the yield of UV / VUV useful radiation continue to improve. The lens 12 consists of UV / VUV transparent material (e.g. made of MgF2 or LiF) and separates the Gas space 9 from the ionization space 14 of the time-of-flight mass spectrometer (TOFMS). The lens 14 focuses the UV / VUV light on the Ionization site 23. When using a needle inlet 15 is located the ionization site 23 behind the inlet needle 15 (in molecular beam formed from the analysis gas) between the Electrodes 18 and 16 of the TOFMS.

As an alternative to the lens 12, a multimicrochannel light guide 24 or 25 can be used. A multi-micro-channel light guide 24 consists of a bundle with a large number of narrow capillaries (analogous to a micro-channel plate). The UV / VUV light that falls through the capillaries can reach the ionization chamber 14, which has a vacuum. If the capillaries are sufficiently long and thin, the gas flow from the gas space 9 through the multimicrochannel light guide 24 into the ionization space 14 is very low (ie the vacuum in 14 is not overloaded too much). The UV / VUV light either falls directly through the clear width of the capillary or is guided through one or more total reflections through the capillaries of the multimicrochannel light guide 24. Furthermore, a multimicrochannel light guide 25 can be used, which allows the transmitted UV / VUV light beam 22 to be focused on the ionization site 23 by a conical taper of the capillary bundle. The main advantage of using multimicrochannel light guides 24 or 25 is that they can transmit VUV light with wavelengths less than 110 nm. Optical lenses 12 or windows for decoupling can only be used up to approximately this wavelength due to the self-absorption of the material (LiF, MgF ₂ ).

The entire optical system for coupling UV / VUV radiation in the ionization chamber 14 in the example presented from the parabolic mirror 11 and the lens 12 or one Multimicrochannel light guide 24 or 25 Combination of a lens 12 or a multimicrochannel light guide 25 with a hollow light waveguide 26, which the UV / VUV light via total reflections directly to ionization site 25 leads, possible.

It is important when designing the coupling of UV / VUV radiation in the ionization chamber 14 that a high radiance is reached at the ionization site 23.

In the example shown in FIG. 1, the inlet of the Analysis gas into the mass spectrometer effusively via an inlet needle 15 [10]. Other sample gas inlet techniques, such as pulsed [11] or continuous supersonic molecular beams [12] can also be used.

FIG. 3 shows a schematic illustration of a time-of-flight mass spectrometer (TOFMS, without representation of the vacuum pumps, of the reflectron ion mirror and other details) with electron beam pumped Excimer-ionization. The UV / VUV light from the electron beam pumped excimer lamp 20 becomes the optical elements described above in the from the inlet needle 15 emerging effusive molecular beam focused. The Voltages in the ion source (simplified here with the electrodes 18, 16 and 17) are chosen so that the ionization space is field free. The by single-photon absorption of VUV photons are not formed by electrical ions Fields affected. The ions formed are thus enriched at and around the ionization site 23. This ion enrichment can be operated for about a few µs, then leave the Ions due to space charge effects and airspeed the particles from the effusive molecular beam again the acceptance volume of the time-of-flight mass spectrometer (i.e. the Volume that can be imaged on the ion detector 21). To detect the enriched ions, the controlled, pulsable high-voltage supply 19 suddenly suitable Potentials applied to the electrodes 18, 16 and 17. The Rising edges of the voltage pulses are usually in the range of a few ns. The ions are accelerated to the detector 21. in the field-free drift space (space between aperture 17 and detector 21) the ions separate according to their mass. The time-of-flight mass spectrum is on the detector 21 with suitable electronics (not shown) registered. Apertures 16 and 17 can be made of perforated screens with or without nets or just consist of networks. The mass resolution and sensitivity in the operation of the TOFMS with ionization described above is limited by continuously shining VUV excimer lamps, because of the continuous operation of the lamp new ions are also formed during the ion withdrawal. These "subsequently" formed ions reach the detector later than ions formed during the enrichment period Mass (i.e. there are peak broadenings and an increased background signal on).

The disadvantages of continuous operation described above The VUV excimer lamp can operate through the pulsed mode the VUV excimer lamp can be avoided.

The electron beam 8 is pulsed (e.g. by pulsed Aperture in the electron gun or through baffles) the film 3 steered. In the case of pulsed operation of the lamp 20 the electron density can be increased thermally without the film 3 to overload. When the electron beam 8 is turned off VUV light emission 22 breaks within 500 to 1000 ns together. This can be exploited to get the ions from the ion source with already significantly reduced VUV light intensity deducted. FIG. 5 shows measured parameters of the VUV excimer lamp ionization TOFMS (prototype) in pulsed operation. The upper trace shows the light pulse from the excimer lamp measured with a photodetector. The middle track shows that Withdrawal pulse from the ion source and the lower trace shows the ion detector signal. Piperidine (85 m / z) and Toluene (92 m / z), the corresponding mass peaks are in the lower one Trace visible.

An important advantage of VUV excimer lamp ionization is that that by the choice of gas in the gas space 9 different wavelengths can be adjusted.

The selectivity of single-photon ionization is based on that only molecules whose ionization energy can be ionized below the photon energy of the incident VUV light is. This allows the ionization to be suppressed of compounds such as oxygen, nitrogen or noble gases, which have very high ionization energies. Hence the VUV ionization very good for on-line analysis of trace compounds from air or process gases (exhaust gases) because the main components the gas mixture cannot be ionized. Farther can also be a by using different wavelengths more precise statement about the composition of the observed Peaks in the mass spectrum can be achieved. For example with photon energies of about 9 eV, an involvement of aliphatic organic compounds excluded on the mass spectrum become. Table 1 shows different gases or Gas mixtures with the corresponding emission wavelengths (maximum values) given. Figure 6 shows the emission profiles of the VUV excimer lamp for argon (left, top) and krypton (left, below). The ionization energies of are also shown Benzene and toluene. On the right are the related ones measured TOFMS mass spectra of a mixture of benzene (92 m / z) and toluene. The argon excimer emission (top) is 128 nm (9.7 eV). Both benzene and toluene are therefore efficiently ionized. The Krypton Excimer Emission (Bottom) is 150 nm (8.2 eV). Here, toluene is right in the center the emission curve, while benzene only from a "shoulder emission" is detected on the high-energy side. In the mass spectrum the toluene peak is therefore orders of magnitude more intense than the benzene peak.

Due to the relatively broad emission spectra (Figure 6, left) the selectivity is only mediocre. With more monochromatic Radiation could be achieved with a higher selectivity. This Can be reached in several ways. By adding certain Gases can emit on a narrow-band emission line be transmitted. For example, with a mixture of Hydrogen and neon have a narrow-band emission at 121.57 nm can be achieved (see Table 1). Alternatively, from the broadband emission spectrum cut a narrow range become. This is e.g. B. by filter / mirror with dichroic coating (interference filter) possible. The Figure 7 shows a first application measurement with the developed Prototype of a time-of-flight mass spectrometer with VUV excimer lamp ionization. Exhaust gas was released via an on-line sampling system a motorcycle (TYPE 43F) via the inlet needle 15 into the mass spectrum admitted. The lamp was operated with argon (128 nm). The figure shows a 3D plot of the mass spectrometric Information (mass, time, intensity) recorded during a starting process of the motorcycle. Different aromatic compounds (Benzene and methylated benzenes) show a highly dynamic, fluctuating time course due to the transient Combustion conditions during the starting phase of the engine. Mass spectrometer with VUV excimer lamp ionization can advantageous for fast time-resolved online analysis of Process gases or used for headspace analysis. Possible Fields of application are, for example, in the food industry (Monitoring of roasting, baking, cooking or Maturation processes etc.) of the chemical industry (monitoring of Syntheses, waste streams, mineral oil processing etc.), in the monitoring of combustion processes and other production processes.

2) Quadrupole mass spectrometer with electron beam pumped UV / VUV excimer lamp

VUV excimer lamp ionization can also be used with other types of mass spectrometers, that don't work pulsed like TOFMS, be used. FIG. 8 shows one according to the invention built-up VUV excimer lamp with optical elements for focusing of the VUV light onto the ionization region of a Quadrupole mass spectrometer. Here is the VUV excimer lamp 20 advantageously operated continuously. The ion source 29 is generated a continuous ion beam. The Andes Quadruplolstäben 27 applied alternating electric fields (from control 28) only allow ions of one mass at a time pass from the ion beam to the detector 30. By changing the alternating fields by means of the controller 28 can be Quadrupole mass spectrometer in succession on a transmission different masses and so can a mass spectrum be included. Possible fields of application of the Quadrupole mass spectrometry with VUV excimer lamp ionization are, for example, in the area of the food industry (monitoring of roasting, baking, cooking or ripening processes etc.) chemical industry (monitoring of syntheses, waste streams, mineral oil processing, etc.) during monitoring of combustion processes and other production processes.

3) Electron beam pumped excimer lamp ionization for mass spectrometers in gas chromatography mass spectrometry (GC-MS) coupling

GC-MS is a standard technique of organic trace analysis. The use of VUV light for ionization for mass spectrometry in gas chromatography mass spectrometry Coupling brings another level of selectivity to the Mass spectrometry. Certain connections with higher levels Ionization energies can be excluded from ionization become. In addition, a fragmentation-free ionization is compared achieved the standard technique of electron impact ionization (EI). Different types of mass spectrometers (ion trap MS, Sector field MS, Qudrupol MS, Flight time MS) can be used for this Purpose.

4) Electron beam pumped UV / VUV excimer lamp for ionization cell detectors

To determine whether organic compounds (and / or inorganic Compounds with a low ionization threshold) in one Air sample, you don't necessarily need a mass spectrometer. It is sufficient to pass through in an ionization space Irradiation of the VUV light to generate ions and electrons and this, for example, via the charge flow using an ammeter 34 or on a resistor using an oscilloscope demonstrated. Figure 9 shows the schematic structure an ionization cell detector with the VUV excimer lamp 20 of the generic type. In the ionization cell (i.e. the ionization space 14) are the electrodes 31 and 32. Between the electrodes 31 and 32 is via a voltage supply 33 a suitable trigger voltage is applied. The sample gas passes between electrodes 31 and 32 via an inlet 15 to the ionization zone. For example via an ammeter 34 can the photocurrent (photo ion current and photo electron current) be detected.

Such a detector has roughly the properties of a flame ionization detector, so it responds to most organic Compounds and on some inorganic species. By the different wavelengths with different gas fillings / optical Systems can be provided a certain selectivity can be achieved. A VUV excimer lamp ionization cell detector can be beneficial for different Applications are used. For example, he can can be used as a detector for gas chromatography. A Another possible application is the use as a sensor for the Occurrence of organic compounds in gas mixtures.

5) Multi-lamp construction with an electron gun for MS and counter

Figure 10 shows an example of the structure of an excimer VUV lamp in which one of the two excimer light sources is used by means of an electron gun 1 36 of the generic type depending on the adjacent electric field pumped between the deflection electrodes 35 and is thus brought to light. The gas spaces 9 are filled of the two excimer light sources with different gases or Gas mixtures (see Tab. 1), the photons have the generated Light of the two excimer light sources is different Photon energy.

Due to the ionization potential, the analysis of a complex sample gas using a light beam from one or the other light source substances in the mass spectrum show or hide. Likewise, by appropriate choice of the Gas or gas mixture and thus the photon energy isobaric Connections can be detected separately.

LIST OF REFERENCE NUMBERS

1

electron gun

2

Electron gun room (vacuum)

3

Membrane (e.g. 1x1 mm ² , thickness = 300 nm made of SiNx ceramic)

4

Getter pump

5

Pump valve

6

gas inlet

7

gas outlet

8th

electron beam

9

Gas space (e.g. filled with 500 mbar argon)

10

Getter cartridge

11

Reflector (e.g. aluminum parabolic mirror with MgF ₂ coating)

12

Lens (e.g. made of MgF ₂ )

13

Volume of gas emitting UV / VUV light

14

ionization chamber

15

Gas inlet needle

16

first trigger electrode

17

second trigger electrode

18

Repeller electrode

19

pulsable power supply for electrodes 16, 17 and 18 and control

20

entire UV / VUV light source

21

detector

22

UV / VUV beam

23

ionization

24

non-focusing multimicro channel light guide

25

focusing multimicro-channel light guide

26

Hollow fiber

27

Quardrupolstäbe

28

Control of the quadrupole ion filter

29

Continuous ion source for the quadrupole mass spectrometer

30

ion detector

31

Electrode of the measuring capacitor (positive voltage, Photelektronenfänger)

32

Electrode of the measuring capacitor (negative voltage, photoio nenfänger)

33

power supply

34

electrometer

35

deflection

36

UV / VUV light source

table

Gas or gas mixture Excited species wavelength bandwidth He Hey ₂ * 60 nm / 80 nm ne Ne ₂ * 83 nm broadband Ar Ar ₂ * 128 nm broadband Kr Kr ₂ * 150 nm broadband Xe Xe ₂ * 172 nm broadband Ne / H ₂ H* 121.57 nm narrow band Ar / Xe
Kr / Xe Xe * 147 nm narrow band Ar / O ₂ O* 130 nm narrow band Ne / Ar / Kr Kr * 124 nm narrow band Ar / F ₂
Ne / F ₂ F ₂ * 157 nm narrow band Ar / F ₂ ArF * 193 nm narrow band

Bibliography:

[1] El-Habachi, A., K. Schoenbach; Appl. Phys. Lett. 72, 22 (1998)

[2] Wieser, J., DE Murnick, A. Ulrich, HA Huggins, A. Liddle, WL Brown; Rev. Sci. Instrum. 68 (3), 1360-1364 (1997)

[3] Salvermoser, M., DE Murnick; Journal of Applied Physics 88 (1), 453-459 (2000)

[4] Wieser, J., M. Salvermoser, LH Shaw, A. Ulrich, DE Murick, H. Dahi; 31, 4589-4597 (1998)

[5] Butcher, DJ, DE Goeringer, GB Hurst; Anal. Chem. 71 (2), 489-496 (1999)

[6] Becker, CH; Fresen. J. Anal. Chem. 341, 3-6 (1991)

[7] Van Bramer, SE, MV Johnston; J. Am. Soc. Mass Spectr. 1 , 419-426 (1990)

[8] Shi, YJ, XK Hu, DM Mao, SS Dimov, RH Lipson; Anal. Chem. 70, 4534-4539 (1998)

[9] Gellert, BB, U. Kogelschatz; Applied Physics B 52 , 14 (1991)

[10] Heger, HJ, R. Zimmermann, R. Dorfner, M. Beckmann, H. Griebel, A. Kettrup, U. Boesl; Anal. Chem. 71, 46-57 (1999)

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[12] Fricke, J .; Phys. Our time 1, 21-27 (1973)

Claims (11)

Ion source where UV / VUV light is used for ionization,
consisting of an ionization room and a UV / VUV excimer light source, the ions being generated with the help of light from a sample gas,
characterized in that the light source consists either of a deuterium tape, a hollow micro cathode lamp, a micro tip lamp, a direct current discharge lamp, a barrier discharge lamp or an electron beam-operated UV / VUV lamp with the following components: a) an electron gun (1), b) a membrane (3) which shoots the space (2) of the electron gun (1) against a gas space (9) and through which the electron beam (8) passes, c) an inert gas or an inert gas-containing gas mixture in the gas space (9), the electron beam (8) passing through the membrane (3) generating light (22) in the gas space (9) and d) optical components (11, 12) for imaging the light emission volume in the ionization space (14). Ion source according to claim 1, characterized by a getter pump (4) in the space of the electron gun (1). Ion source according to claim 1 or 2, characterized by gas inlet and outlet (6, 7). Ion source according to one of Claims 1 to 3, characterized by a getter cartridge (10) which is connected to the gas space (9). Ion source according to one of claims 1 to 4, characterized by at least one electrode for pulsing the electron beam (8) of the electron gun (1). Ion source according to one of Claims 1 to 5, characterized in that the optical components (11, 12) are a light-collecting reflector and a collecting lens or an optical window. Use of the ion source according to one of claims 1 to 6, to generate ions in an ion detector be detected. Use of the ion source according to claim 7, wherein the Ion detection device is a mass spectrometer Use of the ion source according to claim 8, characterized in that a time-of-flight mass spectrometer (TOFMS) is used as the mass spectrometer. Use of the ion source according to claim 8, characterized in that a quadrupole mass spectrometer is used as the mass spectrometer. Use of the ion source according to claim 9, characterized in that the ionization space is additionally irradiated with a laser in order to generate ions by means of a REMPI (resonance enhanced multi-photon ionization) process.

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