Ionization within ion trap using photoionization and electron ionization

1. A mass spectrometer, comprising:

an ion trap having an internal pressure substantially equal to a vacuum pressure and configured to trap an ionized sample, the ion trap including:

a first end cap, wherein the first end cap includes a first aperture, wherein the first aperture is configured to receive electrons from an axial direction for ionizing sample particles by electron ionization within the ion trap; and

a center electrode, wherein the center electrode includes an opening having a larger open area than the first aperture, and wherein the opening is configured to receive photons from a radial direction for ionizing sample particles by photoionization within the ion trap,

wherein the mass spectrometer is configured to alter an electrical signal applied to the ion trap to eject ionized sample particles from the ion trap based on mass-charge ratios of the ionized sample particles.

2. The mass spectrometer of claim 1 , further including an electron source and a photon source.

3. The mass spectrometer of claim 2 , wherein the photon source is a lamp.

4. The mass spectrometer of claim 2 , wherein the photon source is a solid-state diode.

5. The mass spectrometer of claim 1 , wherein the ion trap further includes a second end cap and wherein the center electrode is a ring electrode.

6. The mass spectrometer of claim 1 , wherein the ion trap further includes a second end cap and the center electrode includes two ring electrodes having substantially the same size.

7. The mass spectrometer of claim 1 , wherein the ion trap includes a coating sufficient to reduce electron emission during photoionization.

8. The mass spectrometer of claim 7 , wherein the coating includes a conductive material having a work function higher than energy of the ionizing photons.

9. The mass spectrometer of claim 8 , wherein the ion trap is configured to ionize the sample particles within a trapping field by both electron ionization and photoionization.

10. A method of ionizing a sample within an ion trap, comprising:

directing electrons into the ion trap along an axial direction of the ion trap through a first aperture on a first end cap of the ion trap, wherein the ion trap has an internal pressure substantially equal to a vacuum pressure;

fragmenting at least a portion of the sample into ionized sample particles with the electrons within the ion trap and ejecting the ionized sample particles from the ion trap according to mass-charge ratios of the ionized sample particles;

directing photons into the ion trap along a radial direction of the ion trap through an opening on a center electrode at a different time from the electrons, wherein the opening has a larger open area than the first aperture; and

ionizing at least a portion of the sample into ionized sample particles with the photons within the ion trap and ejecting the ionized sample particles from the ion trap according to mass-charge ratios of the ionized sample particles,

wherein the photons are provided as a series of pulses with a total energy sufficient to ionize the sample.

11. The method of claim 10 , wherein the pulses are provided in vacuum in an ultraviolet wavelength range.

12. The method of claim 10 , wherein the pulses comprise the same amplitude and duration.

13. The method of claim 12 , wherein the pulses have a duration ranging from 2-50 ns.

14. The method of claim 10 , wherein the electrons are provided from a filament.

15. The method of claim 10 , wherein the photons are provided from a laser diode.

16. The method of claim 10 , wherein the photons are provided from a lamp.

17. The method of claim 10 , wherein the pulses include a series of overlapping pulses.

18. The method of claim 17 , wherein the photons are provided from more than one laser diode.

19. The method of claim 10 , wherein the ion trap is a split electrode quadrupole trap.

20. A mass spectrometer comprising:

an ion trap having an internal pressure substantially equal to a vacuum pressure and configured to provide both electron ionization and photoionization within the ion trap, wherein the ion trap includes:

a first end cap having a first aperture configured to receive electrons from an axial direction for electron ionization; and

a center electrode, wherein the center electrode includes an opening having a larger open area than the first aperture and wherein the opening is configured to receive photons from a radial direction for photoionization;

an electron source configured to provide electrons to the ion trap;

a photon source configured to provide photons to the ion trap; and

an ion detector coupled to the ion trap, wherein the ion detector is configured to detect sample ions ejected from the ion trap and to detect sample ions ionized by at least one of the electron source or the photon source,

wherein the mass spectrometer is configured to alter an electrical signal applied to the ion trap to eject the sample ions from the ion trap based on mass-charge ratios of the sample ions.

21. The mass spectrometer of claim 20 , wherein the photon source includes one or more laser diodes configured to provide a series of photon pulses to the ion trap.

22. The mass spectrometer of claim 20 , wherein the ion trap includes a coating configured to reduce electron emission during photoionization.

23. The mass spectrometer of claim 20 , wherein the ion trap is a split electrode quadrupole trap.