Theoretical Study of Valence Shell Excitation by Electron Impact in CCl4

This paper reports a theoretical study of valence shell excitation in CCl4 by high-energy electron impact. Generalized oscillator strengths are calculated for the molecule at the equation-of-motion coupled-cluster singles and doubles level. To elucidate the influence of nuclear dynamics on electron excitation cross-sections, the effects of molecular vibration are included in the calculation. Based on a comparison with recent experimental data, several reassignments of spectral features are made, and it is found that excitations from the Cl 3p nonbonding orbitals to sigma* antibonding orbitals, 7a1 and 8t2, play dominant roles below the excitation energy of similar to 9 eV. Furthermore, the calculations reveal that distortion of the molecular structure due to the asymmetric stretching vibration significantly affects the valence excitations at small momentum transfers, where contributions from dipole transitions are dominant. It indicates that vibrational effects have a considerable influence on Cl formation in the photolysis of CCl4.

Automated summary

This paper presents a theoretical study on valence shell excitation in CCl4 by high-energy electron impact. Generalized oscillator strengths are calculated for the molecule at the equation-of-motion coupled-cluster singles and doubles level, considering the effects of molecular vibration. Based on comparison with recent experimental data, spectral features are reassigned, finding that excitations from the Cl 3p nonbonding orbitals to sigma* antibonding orbitals play dominant roles below the excitation energy of around 9 eV. It is also revealed that molecular structure distortion due to asymmetric stretching vibration significantly affects valence excitations at small momentum transfers.