Laser-Spectroscopic Investigation of Higher Excited Electronic States of the KAr Molecule

Higher excited electronic states of the van der Waals molecule 39KAr have been investigated using a supersonic beam and a two-step excitation. Four hundred seventy Doppler-free lines have been observed in the second step leading to the electronic states 5d2Sigma, 5d2Pi, 5d2Delta, and 7s2Sigma. The spectroscopic parameters of rotation, of spin-orbit splitting, of spin-rotation coupling, and of lambda-type doubling have been determined for altogether 19 vibrational levels of these electronic states. The molecular spin-orbit splitting turns out to be -0.42 cm-1 for 5d2Delta and -0.15 cm-1 for 5d2Pi, which is in fair agreement with the theoretical prediction for a Hund's coupling case a. The vibrational numbering was deduced from theoretical calculations of the interatomic potential. Six vibrational levels have been assigned to the 5d2Delta and the 5d2Sigma state, respectively, allowing a determination of the Dunham coefficients in these two states. For the equilibrium parameters of the 5d2Delta state, we obtain Re = 3.22(15) Å, De = 900(80) cm-1. Copyright 1999 Academic Press.