Absolute partial and total electron-impact ionization cross-sections of the CCl_2F_2 molecule

摘要

A study of the partial ionization cross-sections (ICSs) of the set of ions produced by electron-impact dissociative ionization on halomethane CCl_2F_2 and a sample of the kinetic energy distribution (KED) for the ejected CClF_2~+ ion are reported. Collision experiments were carried out by crossing at right angle two pulsed beams, a supersonic halometane beam and an electron beam with energies in the range from 0 to 100 eV. The ions generated were removed by an appropriate electric field and further characterized in a double focusing time-of-flight mass spectrometer. The CClF_2~+ cation is the fragment ion with the largest partial ICS in the range of electron energies studied, followed by Cl~+, CF_2~+, CF~+, CCL_2F~+, CCl~+, CClF~+, C~+, F~+, Cl_2~+ and CCl_2F_2~+ and some doubly charged ions with smaller intensities. The total ICS curve as a function of the electron-impact energy was obtained by adding up the partial ICS of all the ion fragements. A comparison is made with the computed cross-section by the binary-encounter Bethe (BEB), the Deutsch and Mark (DM), and the modified-additivity-rule (MAR) methods. The experimental results agree best with DM formalism.