Triple Differential Cross Sections for electron impact ionization of methane at intermediate energy

C Granados,J Colgan,C Ning,D Madison,A J Murray,A Sakaamini,M Harvey,M Dogan,E Ali,L U Ancarani

doi:10.1088/1742-6596/1412/15/152086

Abstract

SynopsisIn a joint experimental and theoretical collaboration, triple differential cross sections are presented for electron-impact single ionization of the 1t2 and 2a1 states of CH4 at an incident electron energy of 250 eV. Experimental data from two different laboratories are compared with molecular 3-body distorted wave (M3DW) and generalized Sturmian function (GSF) calculations. Overall, we find a good experiment-experiment, and also a relatively good experiment-theories, agreement. We observe that for the 1t2 state, similarly to ionization of atomic p-states, the peak is sometimes doubled.

Highlights

One of the most fundamental interactions in nature is that of electron-molecule collisions
In this paper we have compared experimental measurements taken at two different laboratories with molecular 3-body distorted wave (M3DW) and generalized Sturmian function (GSF) theoretical calculations, for electron-impact single ionization of the 1t2 and 2a1 states of molecular CH4
Compared to the GSF calculations, the M3DW results are in slightly better agreement with respect to the location of experimental peaks and to the relative magnitude of the Manchester data

Summary

INTRODUCTION

One of the most fundamental interactions in nature is that of electron-molecule collisions. Xu et al.[10] reported experimental and theoretical results for 54 eV electron-impact single ionization of the CH4 HOMO state in both coplanar and perpendicular planes They found qualitative agreement between theory and experiment, the agreement was not as good. It is the purpose of this paper to explore the angular distributions of the TDCS corresponding to the ionization of the HOMO and NHOMO states of CH4, with a focus on the single or double peak structure in the binary region To this end, we consider an incident energy of 250 eV and coplanar asymmetric geometries. The momentum transfer direction is determined by the momentum of the incident electron and the scattered electron, and is given by:

M3DW theory

GSF Theory

Orientation averaging

CONCLUSIONS