There is long standing interest in open shell systems due to their relevance to many facets of combustion and atmospheric chemistry. Given the reactivity of these species and the inherent experimental difficulties in their spectroscopic characterization, theoretical studies can contribute substantially to our overall understanding of these molecules. Moreover, free radicals with their degenerate ground states provide a good testing ground for systems with surface crossings. Such crossings are of great importance, due to their profound influence on the nuclear dynamics. Our group has carried out a series of studies on the spectroscopy of methoxy, an open shell molecule that continues to be subject of both experimental, and theoretical studies. Its vibrational spectrum is strongly influenced by Jahn-Teller coupling, spin-orbit interactions, and Fermi resonances.
We are interested in dynamics occurring on multiple potential surfaces. For the last several years1 we have been studying the methoxy radical. The potential energy surface of this molecule in the ground states is doubly degenerate. If you plot the potential as a function of the two coordinates below
you obtain the below potentials with the conical intersection at the center. In a series of papers we have addressed the dynamics and spectroscopy that occurs for this molecule.
The two spectra below are for CH3O molecule in the normal mode with spin-orbit coupling limit (left) and the fully coupled limit (right). The central plot shows how the levels correlate between the two limits as the Jahn-Teller and anharmonicity increases.