Photodissociation Dynamics of Triatomic van der Waals Molecules

Citation

Cline, Joseph Isaac, III (1988) Photodissociation Dynamics of Triatomic van der Waals Molecules. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/f38f-hb60. https://resolver.caltech.edu/CaltechTHESIS:01182013-155753371

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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