LASER-INDUCED FLUORESCENCE IN KLi

Laser-induced fluorescence spectra of the $B \\rightarrow X$ system of the potassium-lithium molecule have been recorded on a Fourier transform interferometer. The molecules were excited with a tuneable, single-mode cw dye laser operating with Rhodamine 110 or Coumarine 6 dye, and the spectra recorded in the range $12500 - 18500 cm^{-1}$ at a resolution of $0.05 cm^{-1}$. Vibrational levels up to $v = 46$ are observed for the main isotopomer, $^{39}K^{7}Li$. Ground state energies have been fitted to a Dunham polynomial expansion, and also directly to a pointwise potential curve. Both approaches fit the data with a root-mean-square error of $0.005 cm^{-1}$. The data define the ground state potential curve accurately out to about 7 \\AA. The dissociation energy of the ground state $D_{e}$ is estimated to be $D_{e} = 6216 \\pm 2 cm^{-1}$, and the highest vibrational level $v_{max} = 50$ for the main isotopomer. Very weak transitions around $12600 cm^{-1}$ are tentatively assigned as bands of the $2 ^{3}\\Sigma^{+} \\rightarrow 1 ^{3}\\Sigma^{+}$ transition, observed as collisionally induced fluorescence.