Knowledge Bank

A theory for vibration-rotation-large amplitude motion interactions is being developed using curvilinear internal coordinates for the vibrational degrees of freedom. Last year we presented results on the zeroth order separations of vibration from rotation and of the LAM from the other vibrations. Now a Van Vleck transformation through second order has been used to obtain the effective Hamiltonian for the rotation-LAM interactions that has the form All primed terms arise from the interaction with the other vibrations. The geometry dependent coefficients have been calculated for non-linear XY molecules. Applications are underway for $H2O$, treating the bending mode as a large amplitude motion.