Theoretical study on X-ray absorption spectra and bond dynamics for core excitation from valence excited benzoic acids

X-ray absorption spectra (XAS) of the lowest excited singlet, triplet, and ground states (S1, T1, S0-XAS) of benzoic acid and methyl benzoate in the O 1s region were calculated. Resonant core transition to a hole at the highest occupied molecular orbital (HOMO) created by valence excitation was predicted about 3 eV below the lowest peak of S0-XAS but with very weak intensity. A strong peak of the T1-XAS well separated from S0-XAS peaks is found for both molecules so that identification of the core-excitations from the T1 and selective excitation of the T1 become possible. Bond dynamics of oxygen-containing bonds in the potential energy surface of valence and core doubly excited states are estimated by using molecular dynamics simulation. Enhancement in known state-selective dissociation and new type of state selectiteve dissociation are predicted for the core excitations from valence excited state.