DETERMINATION OF THE K-Ar INTERACTION POTENTIAL FOR THE $X\Sigma$ AND $A\Pi$ STATE FROM LASERSPECTROSCOPIC DATA

Abstract

/1/R. Br\""{u}hl et al: J. Chem. Phys. 94 (1991) 5865 and J. Mol. Spectr. 155 (1992) 277Author Institution: Institut f\""{u}r Strahlungs-und Kemphysik, Technische Universitat Berlin HardenbergstrThe interatomic potential of the K-Ar system has been determined for the molecular states $X^{2}\Sigma$ and $A^{2}\Pi$ 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 $B^{2} \Sigma$ state which due to an avoided crossing lowers the energy values of the upper vibrational levels of the $A^{2} \Pi_{1/2}$ 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 $v^{\prime} = 0\ldots 3$ of $X \Sigma$ and $v^{\prime} = 6\ldots 11$ for $A^{2} \Pi$. 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 $A \Pi \rightarrow X \Sigma$ 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 $A^{2} \Pi$, a HFD function for $X^{2}\Sigma$, and a (12.6) Lennard-Jones potential for $B^{2}\Sigma$. Our results for equilibrium distance $R_{e}$ and well-depth $D_{e}$ ar