Photodissociation Dynamics of Triatomic van der Waals Molecules

Author: Cline, Joseph Isaac, III

Year: 1988

Degree: Dissertation (Ph.D.)

Advisor: Janda, Kenneth C.

Committee Members: Kuppermann, Aron; Janda, Kenneth C.; Beauchamp, Jesse L.; Dougherty, Dennis A.

Option: Chemistry

DOI: 10.7907/f38f-hb60

Abstract

The spectroscopy and vibrational predissociation dynamics of triatomic van der Waals molecules are studied experimentally and theoretically at the state-to-state level of detail.

Laser-induced fluorescence spectra of HeCl2 are measured and the geometry and vibrational predissociation rate are obtained by a rotational analysis of the spectra and the determination of homogenous linewidths. A laser pump-probe technique is used to measure the vibrational and rotational state population distribution of the product Cl2. Although the Cl2 fragment has little rotational energy, its rotational distribution is bimodal. A symmetry selection rule for the dissociation results from the symmetry of the He • • • Cl2 van der Waals potential. Quantum mechanical calculations on a realistic potential energy surface are successful in modeling the experimental spectroscopy and dynamics.

The vibrational predissociation dynamics of NeCl2 is also measured using the pump-probe technique. In this case the Cl2 fragment shows significantly more rotational excitation than in the dissociation of HeCl2. The rotational distributions are bimodal and are relatively independent of the energy of the prepared state. The NeCl2 binding energy is estimated from thresholds for the populations of fragment rotational levels.

The vibrational predissociation of NeBr2 is studied by dispersing the fluorescence of the Br2 fragment. The product Br2 is rotationally cold. The closure of vibrational product channels is used to determine the binding energy of the molecule.

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