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Abstract
Absolute cross sections, differential in angle and ejection energy, for electron production by electron, proton and atomic hydrogen impact on water vapor have been measured using electrostatic analysis and counting of individual secondary electrons. The range of projectile energies was 15-150 keV for proton, 20-150 keV for neutral hydrogen and 50-2000 eV for electron impact. The experiment was performed under static gas conditions.
In the case of proton and neutral hydrogen impact, the ejection angle ranged from 10(DEGREES) to 160(DEGREES) and the ejected electron energies were measured from 1.0 to 300 eV. The higher energy proton impact data was compared with different theoretical calculations; i.e. the DDCS-MT treatment of B. Senger with and without the Salin's factor and a binary encounter calculation for singly differential cross sections. The results were also compared with the available experimental data at higher impact energies.
In the case of electron impact, the secondary electrons were detected over both the ejected and scattered electron regions with angles ranging from 15(DEGREES) to 150(DEGREES). The data were compared with the available doubly differential and total experimental measurements in the literature. Also a comparison is made between the present measurement and the Mott calculations and with the semi-empirical calculations of Paretzke.
A comparative study was done to point out similarities and differences between the three different projectiles. The study showed that neutrals and protons act similarly in the hard collision region, while the neutrals and electrons show similar behavior at the very low ejected electron energies. The spectra from neutral impacts showed the effect of the additional mechanisms of the electron loss to the continuum and the screening of electrons.
