Study on the effect of external electric field excitation on methane

Abstract

The present paper is devoted to the calculation of transition wavelengths, os cillator strengths f, Einstein An0 and B0n coefficients of methane from ground state Ｘ～lＡl to the first six di fferent excited states by employing density functional theory and single substitute con figuration interaction (CIS) approach with basis sets 6-311++G**. At the same time, the excited states of methane under an external electric field are i nvestigated. It is shown that the total energy of the system has little change d, and simultaneously the HOMO-LUMO gaps become small and the Fermi levels dec lines slightly as the external electric field intensity become strong. The trans ition between ground state Ｘ～lＡl and the high-excited state of methane is easy bring about.