Equilibrium geometries, adiabatic excitation energies and intrinsic C=C/C-H bond strengths of ethylene in lowest singlet excited states described by TDDFT

Abstract

Seventeen singlet excited states of ethylene have been calculated via time-dependent density functional theory (TDDFT) with the CAM-B3LYP functional and the geometries of 11 excited states were optimized successfully. The local vibrational mode theory was employed to examine the intrinsic C=C/C-H bond strengths and their change upon excitation. The natural transition orbital (NTO) analysis was used to further analyze the C=C/C-H bond strength change in excited states versus the ground state. For the first time, three excited states including Π'y → 3s, Π'y → 3py and Π'y → 3pz were identified with stronger C=C ethylene double bonds than in the ground state.