Electron transmission spectroscopy of some inorganic and organic molecules
An electron spectrometer was built in our laboratory to study the interaction of
low energy ( 0.3 to 10 eV ) electrons with neutral molecules.
The helium resonance at 19.3 eV was used to determine the energy resolution
of the electron beam, and the 2.1 eV molecular nitrogen resonance to calibrate the
energy scale of the incident electron beam.
Total absolute cross sections were measured for the following molecules:
molecular nitrogen, carbon monoxide, carbon dioxide, sulphur dioxide; also recorded
was their electron affinity and resonant vibrational levels arising from temporary
formation of negative ion states.
Relative cross sections , resonant vibrational structures and electron affinities
were determined for the following molecules: benzene, furan, pyrrole; ethylene,
propene, butene, pentene, hexene; cyclopentene, cyclohexene, cycloheptene,
cyclooctene. Comparison between these measurements and the most recent
theoretical calculations and experimental data of other laboratories are presented.
The spectrometer was modified by incorporating a manometer for the purpose
of making accurate pressure measurements inside the collision chamber and
interfaced with a new computer containing the appropriate software to calculate the
electron cross section of molecules in the gas phase. Also measured, for the first time
in our laboratory, the absolute total electron cross sections of N2, CO, CO2 and SO2,
the latter never having been measured before anywhere.
The electron beam resolution was improved by incorporating into the
spectrometer an additional 1270 momentum cylindrical selector in tandem with the
existing monochromator but having separate controls.
The previously published results of C6H6, N2, C2H4, were remeasured and
inaccuracies were discovered in this data. In addition, the electron affinities of a
complete series of related compounds-: linear and cyclic alkenes - were measuredf or
the first time and to the best of the author's knowledge the results are original and do
not appear elsewhere.