Free Jet Expansion Laser Spectroscopy of van der Waals Molecules Containing Ne and Br₂

Citation

Swartz, Barry Allan (1984) Free Jet Expansion Laser Spectroscopy of van der Waals Molecules Containing Ne and Br₂. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/mp06-am61. https://resolver.caltech.edu/CaltechTHESIS:10312018-092920492

Abstract

Fluorescence excitation spectra of complexes of Ne and Br₂ containing up to four Ne atoms have been measured. The van der Waals molecules were synthesized in a free jet expansion and excited with tunable excimer-pumped dye laser radiation. Features attributable to van der Waals complexes by virtue of their intensity dependences on molecular beam stagnation pressure appear shifted to the blue of band origins of the B³Πo⁺_g ← X1Σ⁺_g transition of all three isotopic species of Br₂. Spectra were recorded for transitions (11-0) through (30-0) of Br₂ which show that the specral shifts of the complexes relative to the Br₂ band origins increase with increasing v'. NeBr₂ shifts range from 5.5 to 8.8 cm^-1. The spectral widths of the van der Waals features also increase with v' from a laser bandwidth limited value of 0.10 cm^-1 for NeBr₂ (16-0) to 3.1 cm^-1 for (27-0). This indicates a greater than order of magnitude change in the lifetimes of these complexes with level of vibrational excitation which is disucssed in relation to recent theories on the dynamics of weakly bound systems. Estimates of 73 and 64 cm^-1 were obtained for the van der Waals bond dissociation energy for the ground and excited electronic states, respectively.

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