Photoemission induced electron ionization
View Patent ↗A monitor that can detect at least one molecule. The monitor includes a housing with a passage that can receive a sample, and a photocathode that is located within the housing. The monitor also includes a first ultraviolet light source that can direct ultraviolet light onto the photocathode to create electrons that ionize molecules within the sample, and a detector that is coupled to the housing to detect at least one ionized molecule. The monitor enables electron ionization (EI) of a sample for chemical analysis without the disadvantages of current methods that use a hot filament or other thermal cathode devices.
1. A monitor that can detect at least one molecule, comprising:
a housing with a passage that can receive a sample;
a photocathode located within the housing;
a first ultraviolet light source that can direct ultraviolet light onto the photocathode to create electrons that ionize molecules within the sample; and,
a detector coupled to said housing to detect at least one ionized molecule.
2. The monitor of claim 1 , wherein said housing includes a first chamber where the electrons are created and a second chamber where the sample is ionized.
3. The monitor of claim 1 , wherein said housing includes a chamber where the electrons are created and the sample is ionized.
4. The monitor of claim 3 , wherein the ultraviolet light travels across said chamber and strikes said photocathode.
5. The monitor of claim 1 , further comprising at least one electrode that creates a voltage potential that moves the electrons.
6. The monitor of claim 5 , wherein the electrode is curved.
7. The monitor of claim 1 , wherein said photocathode is located at an oblique angle relative to said first ultraviolet light source.
8. The monitor of claim 1 , wherein said photocathode is curved.
9. The monitor of claim 1 , wherein said housing includes a window and said first ultraviolet light source is attached externally to said housing and the ultraviolet light travels through said window.
10. The monitor of claim 1 , wherein negative ions are formed.
11. The monitor of claim 10 , further comprising at least one electrode that causes the electrons and ionized molecules to move in a same direction.
12. The monitor of claim 1 , further comprising a second light source that emits light at a different energy level than the ultraviolet light emitted by the first ultraviolet light source.
13. The monitor of claim 12 , wherein the second light source is a ultraviolet light source.
14. A method for detecting a molecule in a sample, comprising:
directing ultraviolet light onto a photocathode to create electrons;
ionizing molecules of a sample with the photoemitted electrons; and,
moving the ionized molecules to a detector to detect at least one ionized molecule.
15. The method of claim 14 , wherein the photoemitted electrons are accelerated to energies that ionize the molecules by electron ionization.
16. The method of claim 14 , wherein the electrons attach to the molecules to form negative ions.
17. The method of claim 14 , further comprising varying the energy of the photoemitted electrons to vary fragmentation of the ionized molecules.
18. The method of claim 14 , further comprising increasing an electron flux with an electron amplifier.