TE'08		5min5:24

L. A. KALEDIN, A. L. KALEDIN AND M. C. HEAVEN, Department of Chemistry, Emory University, Atlanta, GA 30322.

Laser absorption spectrum of the LaF B¹ -X¹⁺ (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 LaF₃ powder to 1900 K. 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 r_e (in nm) for the X¹⁺ state are:

TABLE

Rotational perturbations were evident in the B¹ v' =1,v' =2,and v' =3 levels. The pattern of the B¹ state perturbations was shown to be a consequence of the interaction with the c₁³₁ state by using the experimental value of \omega_e =450 cm^-1 (see Reference) and estimated value of \omega_ex_e =3.5 cm^-1 for the triplet state. The principal new results to emerge from this investigation are the determination of the equilibrium constants for the B¹ and X¹⁺ states of LaF.

Work supported by AFOSR under grant F19628-90-C-025.