Knowledge Bank

The interatomic potential of the K-Ar system has been determined for the molecular states $X2\Sigma$ and $A2\Pi$ from laserspectroscopic data using a fully quantum-mechanical approach and using the same analytical functions for the potential as in previous cases /1/. For the first time, we were able to take approximately into account the $B2\Sigma$ state which due to an avoided crossing lowers the energy values of the upper vibrational levels of the $A2\Pi 1/2$ state. Our experimental data have been derived from a high-resolution absorption spectrum due to the transition $A\Pi \leftarrow X\Sigma$. They consist of rovibrational energy values for $v\prime =0\dots 3$ of $X\Sigma$ and $v\prime =6\dots 11$ for $A2\Pi$. The molecular energy levels could accuratryly be referred to the atomic energy scale by observation of the onset of predissociation in the $A\Pi 3/2$ state. In addition, the spectral distribution of the fluorescence light $A\Pi \to X\Sigma$ has been recorded providing information on the repulsive part of the $X\Sigma$ potential. We obtain agreement with all experimental data by using a Tang-Toennies function for $A2\Pi$, a HFD function for $X2\Sigma$, and a (12.6) Lennard-Jones potential for $B2\Sigma$. Our results for equilibrium distance $Re$ and well-depth $De$ are