Electron impact partial ionization cross sections of methyl alcohol up to 5 keV using the mass spectrometry data

The electron impact partial ionization cross sections (PICSs) of methyl alcohol fragments are reported from ionization threshold to 5 keV. The calculations employ use of electron impact mass spectrometry data and a modified form of binary-encounter-Bethe (BEB) model. In the modified-BEB approach, the binding energy of each occupied molecular orbital is incremented by an amount such that the highest occupied molecular orbital reflects the appearance potential of a particular fragment. The PICSs are then obtained by appropriately scaling the cross section data using the branching ratios (BR). The BRs can either be obtained from the cross section data or using the mass spectrometry data at an energy at which the mass spectrum is recorded. The PICSs are summed to obtain the total ionization cross sections (TICS) of the methyl alcohol. The results are in good agreement with the experimental results and are superior to the existing theoretical results. A simple approach like this in conjunction with mass spectrometry would be of immense help in modeling and interpretation of ionization data. The study reveals the need for more consistent ion energetics and mass spectrometry data for an accurate modeling of PICSs