Terrance J. Codd

Spectroscopic studies of the Ã-X̃ electronic spectrum of the β-hydroxyethylperoxy radical: structure and dynamics.

The jet-cooled Ã-X̃ near IR origin band spectra of the G(1)G(2)G(3) conformer of four β-hydroxyethylperoxy isotopologues, β-HEP (HOCH(2)CH(2)OO), β-DHEP (DOCH(2)CH(2)OO), β-HEP-d(4) (HOCD(2)CD(2)OO), and β-DHEP-d(4) (DOCD(2)CD(2)OO), have been recorded by a cavity ringdown spectrometer with a laser source linewidth of ~70 MHz. The spectra of all four isotopologues have been analyzed and successfully simulated with an evolutionary algorithm, confirming the cyclic structure of the molecule responsible for the observed origin band. The analysis also provides experimental à and X̃ state rotational constants and the orientation of the transition dipole moment in the inertial axis system; these quantities are compared to results from electronic structure calculations. The observed, broad linewidth (Δν > 2 GHz) is attributed to a shortened lifetime of the à state associated with dynamics along the reaction path for hydrogen transfer from the OH to OO group.

ROVIBRONIC ANALYSIS OF THE e′ BANDS IN THE Ã2 E′′ STATE OF NO3 RADICAL

The vibronic structure of the NO3 radical has been the subject of much recent research in our group.a We have also collected several high resolution spectra of transitions to the Ã2E′′ state. Parallel bands, with a′′ 1 symmetry, have been satisfactorily fit using an oblate symmetric top Hamiltonian with spin rotation. Some lines were seen to be perturbed and it is likely that this is the result of random perturbations from levels originating from the ground electronic state. The perpendicular bands, which have e′ symmetry, are not satisfactorily described using this Hamiltonian. In particular the rotational structure of the e′ levels has many more transitions than in the oblate top model predicts. For this reason we have developed two different rovibronic Hamiltonians for the analysis of the vibronically degenerate levels. Both include spin-orbit, coriolis, spin-rotation, and Jahn-Teller distortion terms. However, they are derived starting from two different limiting cases. In Case 1 the Hamiltonian is built by assuming first a D3h configuration and then perturbations are added. Case 2 starts at the statically distorted, low symmetry geometry and introduces interactions among the vibronic levels. In the case of Jahn-Teller coupling that is neither very weak nor very strong these models should both adequately describe the observed spectra. These models and preliminary analysis of several e′ bands are presented.