State-to-state photoionization dynamics of nitrogen dioxide

Patrice Bell, Purdue University

Abstract

Photoionization dynamics of high energy Rydberg states of NO2 provide a window on the anharmonic coupling that drives energy transfer among vibrational degrees of freedom of the NO2+ core. This coupling directs the ionization mechanism of superexcited NO2. Work presented in this thesis uses multistep, multiresonant excitation to overcome the Franck Condon barrier to bent-to-linear excitation of the molecule. These Rydberg states can be modeled as a positive ion core with a loosely bound electron. We examine both the Rydberg core and electron using mass spectrometry and photoelectron spectroscopy respectively. We are able to probe autoionizing Rydberg states to show the normal mode dependence of vibrational autoionization of NO2. These experiments picture of the state-to-state photoionization dynamics of NO2. We also investigate vibrational state selection pathways leading to final quantum states of NO 2+ using multi-resonant ionization. Combining this laser excitation scheme with photoelectron spectroscopy provides a direct measurement of the final product state distribution. In addition to the electron kinetic energy of the final states, the intensities of resonances reveal the relative populations of final states. We find that ionization is preferred by transfer of vibrational energy from the symmetric stretching mode. Results point to highly selective, ion state preparation routes via selected Rydberg states.

Degree

Ph.D.

Advisors

Grant, Purdue University.

Subject Area

Chemistry

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