Studies of the photoionization cross sections of CH4

Abstract

We present cross sections and asymmetry parameters for photoionization of the lt 2 orbital of CH 4 using static-exchange continuum orbitals of CH/ to represent the photoelectron wave function. The calculations are done in the fixed-nuclei approximation at a single internuclear geometry. To approximate the near-threshold behavior of these cross sections, we assumed that the photoelectron spectrum is a composite of three electronic bands associated with the Jahn-Teller components of the distorted ion. The resulting cross sections reproduce the sharp rise seen at threshold in the experimental data and are in good agreement with experiment at higher energy. The agreement between the calculated and measured photoelectron asymmetry parameters is, however, less satisfactory.

Analysis of electron impact ionization properties of methane

“… Van Dishoeck et al [1980] derived ab initio correlation diagrams for dissociative ionization of methane. Braunstein et al [1988] calculated cross section and asymmetry parameter for the (1t 2 ) −1 state. Stener et al [2002] performed similar calculation with time‐dependent density function theory.…”

Photoionization cross sections and asymmetry parameters for silane

“…In fact, the only molecular system with T d symmetry for which theoretical results of photoionization cross sections have been reported is methane. 21 In that study the calculated cross sections show a sharp rise near the ionization threshold which was attributed to the Jahn-Teller distortion of the ion.…”

Photoionization of C2F4 in the VUV region

“…Details of the ISVM have been given elsewhere 7, 10; only its essential aspects will be outlined here. The photoelectron differential cross sections averaged over molecular orientations are given by where σ ( L,V ) is the total photoionization cross section, obtained with the length ( L ) or velocity ( V ) form of the dipole moment operator.…”

“…The ISVM has been used in photoionization calculations since the early 1980s. First applications of this method were in the studies of photoionization of linear 7–9 and small polyatomic 10 molecules. More recent applications of the ISVM to molecular photoionization studies include those of C 2 H 2 , N 2 , O 2 , CO 2 , SiH 4 , CF 4 , and GeH 4 11–19.…”