Dynamical chirality and the quantum dynamics of bending vibrations of the CH chromophore in methane isotopomers

The time-dependent quantum dynamics of the CH chromophore is investigated b y calculations of the wave packet evolution after coherent excitation of th e bending modes using realistic potential energy surfaces and electric dipo le moment functions for the methane isotopomers CHD3, CHD2T, and CHDT2 deri ved previously from ab initio calculations and high-resolution spectroscopi c information. Results include discussions on different excitation pathways depending on the bending direction in an internal coordinate frame, the ro le of quasiclassical and delocalized intramolecular vibrational redistribut ion on these processes, and a possibility of controlling the dynamics by lo calization of the wave packet motion in subspaces of the relevant configura tion space. Bending excitation is also used to generate dynamical chirality , which is quantified by the enantiomeric excess. The subsequent free evolu tion of the wave packet after generation of a chiral molecular structure co rresponds to a stereomutation reaction on the femtosecond time scale superi mposed by a racemization reaction, which is understood as arising from quan tum delocalization effects due to intramolecular vibrational redistribution .