Discrimination of 1,1-difluoroethylene nuclear spin isomers in the presence of non-adiabatic coupling terms

Abstract

The possibility to discriminate the ortho and para nuclear spin isomers of 1,1-difluoroethylene via their excited state dynamics is studied using wavepacket propagations including non-adiabatic couplings. The two nuclear spin isomers are connected via a torsional motion around the double bond. Photo-excitation induces a different interference pattern, with different torsional periods – a fact that can be exploited to distinguish, and eventually separate the nuclear spin isomers using femtosecond pump-probe experiments. The inclusion of non-adiabatic couplings results in a slowdown of the wavepacket, increasing the torsional periods of the nuclear spin isomers.