Systematics of the gradient on the resonant core-hole state

Systematics of the gradient on the resonant core-hole state in the Franck-Condon region were investigated theoretically. The steepest gradient for a target bond in the resonant core-excited states becomes more negative with increasing sum of atomic numbers of the atom in the bonded pair and increasing bond order for the associated chemical bond. Gradients for molecules that include conjugated double bonds such as butadiene and hexatriene were also examined at the lowest core-hole state. The gradients for the double bond become negative while that those for the single bond become positive with few exceptions, suggesting that a fragment from a target molecule gains its initial momentum at the multiple bond.