We report an experimental and theoretical investigation of electron-impact single ionization of the highest occupied molecular orbital 1t2 and the next highest occupied molecular orbital 2a1 states of CH4 at an incident electron energy of 250 eV. Triple differential cross sections measured in two different laboratories were compared with results calculated within the molecular 3-body distorted wave and generalized Sturmian function theoretical models. For ionization of the 1t2 state, the binary peak was observed to have a single maximum near the momentum transfer direction that evolved into a double peak for increasing projectile scattering angles, as has been seen for ionization of atomic p-states. A detailed investigation of this evolution was performed. As expected because of its s-type character, for ionization of the 2a1 state, only a single binary peak was observed. Overall, good agreement was found between experiment and theory.



Research Center/Lab(s)

Center for High Performance Computing Research


National Science Foundation (U.S.)


This work was partly supported by the US National Science Foundation under Grant. No. PHY-1505819 and by the National Natural Science Foundation of China under Grant No. 11174175.

Keywords and Phrases

Electron energy levels; Molecular orbitals, Electron impact-ionization; Highest occupied molecular orbital; Incident electrons; Intermediate energies; Single ionization; Sturmian functions; Theoretical investigations; Triple differential cross sections, Impact ionization

International Standard Serial Number (ISSN)

0021-9606; 1089-7690

Document Type

Article - Journal

Document Version

Final Version

File Type





© 2019 The Authors, All rights reserved.

Publication Date

01 May 2019

Included in

Physics Commons