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Dynamics of rotationally-resolved multiphoton ionization processes in molecules

Thesis/Dissertation ·
OSTI ID:6054384

This dissertation presents the results of studies of several rotationally-resolved resonance enhanced multiphoton ionization (REMPI) processes in some simple molecular systems. The objective of these studies is to quantitatively identify the underlying dynamics of this highly state-specific process which utilizes the narrow bandwidth radiation of a laser to ionize a molecule by first preparing an excited state via multiphoton absorption and subsequently ionization that state before it can decay. Coupled with high-resolution photoelectron spectroscopy, REMPI is clearly an important probe of molecular excited states and their photoionization dynamics. A key feature of these studies is that they are carried out using accurate Hartree-Fock orbitals to describe the photoelectron orbitals of the molecular ions. Studies reported here include investigations of (i) ionic rotational branching ratios and their energy dependence for REMPI via the A{sup 2}{Sigma}{sup +}(3s{sigma}) and D{sup 2}{Sigma}{sup +}(3p{sigma}) states of NO, (ii) the influence of angular momentum constraints on branching ratios at low photoelectron energies for REMPI via low-J levels of the resonant intermediate state, (iii) the strong dependence of photoelectron angular distributions on final ionic rotational state and on the alignment in REMPI of the A{sup 2}{Sigma}{sup +} state of NO, (iv) vibrational state dependence of ionic rotational branching ratios arising from rapid orbital evolution in resonant states (v) the influence of rovibronic interactions on the rotational branching ratios seen in REMPI via the D{sup 2}{Sigma}{sup +}(3p{sigma}) state of NO.

Research Organization:
California Inst. of Tech., Pasadena, CA (USA)
OSTI ID:
6054384
Country of Publication:
United States
Language:
English