UNDERSTANDING CH$_5^+$ SPECTROSCOPY FROM A PARTICLE-ON-A-SPHERE MODEL

Author Institution: JILA, Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309Due to the low barrier to H rearrangement in CH$_5^+$, a good approximation is to separate the angular and radial H coordinates. By fixing R$_{CH}$ at a constant value, the 15 degree-of-freedom problem becomes a more computationally feasible 10 degree-of-freedom problem. The reduced dimensional problem is well suited for capturing the essential low energy, large amplitude bending/rotation dynamics. The "particle-on-a-sphere" (POS) model, which has been shown to provide good experimental agreement in XH$_n$ (n=2-4) systems is extended to accommodate a 5 hydrogen system. Building on past success with the XH$_n$ systems, we use the XH$_5$ POS model to calculate the patterns of the low J rovibrational spectrum, facilitating the understanding of the jet-cooled CH$_5^+$ spectrum