Accession Number:

ADA183365

Title:

Electron Impact Phenomena in VUV Photoionization Mass Spectroscopy

Descriptive Note:

Interim technical rept.

Corporate Author:

ARIZONA UNIV TUCSON DEPT OF CHEMISTRY

Personal Author(s):

• Huth, Thomas C.
• Denton, M. B.

Report Date:

1987-05-01

Pagination or Media Count:

25.0

Abstract:

Electron impact ionization arising from acceleration of stray electrons in the ion source is a major interference in photoionization mass spectrometry with vacuum ultraviolet sources. Results are presented which show that most of this ionization is caused by low energy secondaries generated when stray primaries are collected by the ion source electrodes. The primaries are produced mainly by interaction of scattered VUV radiation with metal surfaces. The low energy stray electron impact process can produce molecular ions as the only detectable electron impact features in the photoionization mass spectrum, especially for aromatic compounds. These features are not immediately distinguishable from photoions in the spectrum. When time of flight mass analysis is employed, the distinction can be made simply through adjustment of ion source conditions. The method for accomplishing this is described and demonstrated.

Descriptors:

• *ELECTRONS
• *ELECTRON IMPACT SPECTRA
• *AROMATIC COMPOUNDS
• *VACUUM ULTRAVIOLET RADIATION
• *IONIZATION
• METALS
• SOURCES
• RADIATION
• SCATTERING
• PHOTOIONIZATION
• MOLECULAR IONS
• MASS SPECTROMETRY
• MASS SPECTRA
• ION SOURCES
• ION SELECTIVE ELECTRODES
• IMPACT
• LOW ENERGY
• FLIGHT
• ACCELERATION
• MASS
• MASS SPECTROSCOPY
• SURFACES

Subject Categories:

• Physical Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE