Theoretical study on ultrafast intersystem crossing of chromium(III) acetylacetonate

Abstract

In the relaxation process from the ^4T_[2g] state of chromium(III) acetylacetonate, Cr^III(acac)_3, ultrafast intersystem crossing (ISC) competes with vibrational relaxation (VR). This contradicts the conventional cascade model, where ISC rates are slower than VR ones. We hence investigate the relaxation process with quantum chemical calculations and excited-state wavepacket simulations to obtain clues about the origins of the ultrafast ISC. It is found that a potential energy curve of the ^4T_[2g] state crosses those of the ^2T_[1g] states near the Franck–Condon region and their spin–orbit couplings are strong. Consequently, ultrafast ISC between these states is observed in the wavepacket simulation.