A rigorous full-dimensional quantum dynamics study of tunneling splitting of rovibrational states of vinyl radical CH.

We report a rigorous quantum mechanical study of the rovibrational energy levels of vinyl radical CH. The calculations are carried out using a real two-component multi-layer Lanczos algorithm in a set of orthogonal polyspherical coordinates based on a recently developed accurate ab initio potential energy surface of CH. All well converged 158 vibrational bands up to 3200 cm are determined, together with a comparison to previous calculations and experimental results. Results show a remarkable multi-dimensional tunneling effect on the vibrational spectra of the radical. The vibrational tunneling splitting is substantially different from that of previous reduced dimensional calculations. The rotational constants of the fundamental vibrational bands of CH are also given. It was found that the rovibrational states are strongly coupled, especially among those bending vibrational modes. In addition, the perturbative iteration approach of Gruebele has been extended to assign the rovibrational energy levels of CH without the requirement of explicit wavefunctions.