10min:

A. J. ROSS, F. MARTIN, P. CROZET AND M. AUBERT-FRÉCON, Laboratoire de Spectrométrie Ionique et Moléculaire (UMR 5579 CNRS), Bâtiment A. Kastler, Université Lyon I, Domaine Scientifique de la Doua, 69622 Villeurbanne Cedex, France; P. KOWALCZYK, Institute of Experimental Physics, Warsaw University , Ul. Hoza 69, 00-681 Warsaw, Poland; W. JASTRZEBSKI, Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland.; AND A. PASHOV, Universität Hannover, Institut für Quantenoptik, Welfengarten 1, 30167 Hannover, Germany.

Laser-induced fluorescence spectra of the B 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, ³⁹K⁷Li.

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 Å. 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 +} 1~^{3 +} transition, observed as collisionally induced fluorescence.