LASER ABSORPTION SPECTROSCOPY OF LaF: ANALYSIS OF THE $B^{1}\Sigma^{+}$ TRANSITION
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Date
1996
Journal Title
Journal ISSN
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Publisher
Ohio State University
Abstract
Laser absorption spectrum of the LaF $B^{1}\Pi-X^{1}\Sigma^{+}$ (2,0), (1,0), (2,1), and (3,2) bands was recorded. Gas phase LaF was obtained by heating a mixture of a 0.2 g of La metal and 0.3 g of $laF_{3}$ powder to 1900K. In order to modulate the absorption signal, the concentration of LaF was varied by passing a 25 kHz discharge (80-100W, 0.5A peak current) through the vapor. Under these conditions the Tantalum heating tube used to vaporize the sample also acted as a hollow cathode. The B-X band system was observed previously In analyzing the spectrum, we have combined absorption data with that from the Reference. Accurate molecular constants (in $cm^{-1}$) and internuclear distance $\tau_{e}$ (in nm) for the $X^{1}\Sigma^{+}$ state are:$$\omega_{e}=573.318, \omega_{e}x_{e}=2.18, B_{e}=0.246411(15), \alpha_{e}=1.251(15)\times10^{-3}, \tau_{e}=0.20232.$$ Rotational perturbations were evident in the levels. The pattern of the state perturbations was shown to be a consequence of the interaction with the state by using the experimental value of $\omega_{e}=450$ $cm^{-1}$ (see Reference) and estimated value of $\omega_{e}x_{e}$ $cm^{-1}$ for the triplet state. The principal new results to emerge from this investigation are the equilbrium constants for the $B^{1}\Pi$ and $X^{1}\Sigma^{+}$ states of LaF.
Description
Work supported by AFOSR under grant F19628-90-c-025. $^{a}$ H. Schall, C. Linton, and R. W. Field J. Mol. Spectrose. 100, 437-448 (1985): B. Simard and A. M. James, J. Chem. Phys. 97, 4669-4675 (1992)
Author Institution: Department of Chemistry, Emory University
Author Institution: Department of Chemistry, Emory University