Knowledge Bank

Laser-induced fluorescence spectra of the $B\to X$ 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 $12500-18500cm-1$ at a resolution of $0.05cm-1$. Vibrational levels up to $v=46$ are observed for the main isotopomer, $\mathrm{<mrow\; data-mjx-texclass="ORD">39</mrow>}K7Li$. 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 $0.005cm-1$. The data define the ground state potential curve accurately out to about 7 \AA. The dissociation energy of the ground state $De$ is estimated to be $De=6216\pm 2cm-1$, and the highest vibrational level $vmax=50$ for the main isotopomer. Very weak transitions around $12600cm-1$ are tentatively assigned as bands of the $23\Sigma +\to 13\Sigma +$ transition, observed as collisionally induced fluorescence.