title: Communication: Effective spectroscopic Hamiltonian for multiple minima with above barrier motion: Isomerization in HO(2).
abstract: We present a two-dimensional potential surface for the isomerization in the hydroperoxyl radical HO(2) and calculate the vibrational spectrum. We then show that a simple effective spectroscopic fitting Hamiltonian is capable of reproducing large scale vibrational spectral structure above the isomerization barrier. Polyad breaking with multiple resonances is necessary to adequately describe the spectral features of the system. Insight into the dynamical nature of isomerization related to the effective Hamiltonian is gained through classical trajectories on the model potential. Contrary to physical intuition, the bend mode is not a "reaction mode," but rather isomerization requires excitation in both stretch and bend. The dynamics reveals a Farey tree formed from the 2:1 and 3:1 resonances, corresponding to the resonance coupling terms in the effective Hamiltonian, with the prominent 5:2 (2:1+3:1) feature dividing the tree into parts that we call the 3:1 and 2:1 portions.
authors.affiliation: Department of Chemistry and Institute of Theoretical Science, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: George L
authors.initials: GL
authors.lastname: Barnes
authors.forename: Michael E
authors.initials: ME
authors.lastname: Kellman
mesh_terms: D007536:Isomerism; D008956:Models, Chemical; D010545:Peroxides / Q000737:chemistry*; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D014732:Vibration
chemical_list: D010545:Peroxides; C049375:perhydroxyl radical