Experimental and multichannel quantum defect theory analysis of autoionizing states in the high Rydberg bending modes of the formyl radical
Abstract
The research presented in this thesis characterizes the autoionizing high Rydberg states of the formyl radical via multiphoton laser spectroscopy and dedicated theoretical calculations. The purpose of this research is to enhance the fundamental knowledge of highly excited states as well as provide a fully characterized system for use in the advancement of relevant theories describing polyatomic excited states. To this end, the ionization-detected absorption spectra of autoionization Rydberg states have been systematically gathered from first-photon-prepared origin states from N′ = 0 to 5. Sharp second-photon resonances are compared to characterize the resonances in terms of good total angular momentum quantum number, N. Rydberg simulations display a remarkable fit while employing a limited basis of constant quantum defects and experimentally determined convergence limits. The splitting patterns of Rydberg orbital and core rotational angular momentum interactions assign certain features to a predominant Hund's case (b) coupling scheme. Increasing the vibrational amplitude minimally varies the constant quantum defects employed in the simulations, with a tendency toward a blue shift in the low n region as a result of decoupling. Fano-Beutler line shapes characterize the mixing of the ionization continuum with the discrete autoionizing states embedded within. Large Fano q-parameters (generally greater than 30) determined for (010) and (020) denote transitions to the discrete states dominate this process, while (030) displays increased asymmetry due to the strong R-dependence of the off diagonal elements of the quantum defect reaction matrix. The constant quantum defects of the Rydberg simulations are indicative of the quantum defects employed in multichannel quantum defect theory calculations. Systematic calculations have confirmed most case (b) splitting assignments from the Rydberg analysis. The inclusion of s-d mixing in the calculations reassigns the low intensity doublet pairs from its pure d-orbital assignment in the Rydberg analysis.
Degree
Ph.D.
Advisors
Grant, Purdue University.
Subject Area
Chemistry
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