Laser-spectroscopic investigation of higher excited electronic states of the KAr molecule

Higher excited electronic states of the van der Waals molecule (KAr)-K-39 h ave been investigated using a supersonic beam and a two-step excitation. Fo ur hundred seventy Doppler-free lines have been observed in the second step leading to the electronic states 5d(2)Sigma, 5d(2)II, 5d(2)Delta, and 7s(2 )Sigma. The spectroscopic parameters of rotation, of spin-orbit splitting, of spin-rotation coupling, and of h-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 5d(2)Delta and -0.15 cm(-1) for 5d(2)II, which is in fair agreement with the theoretical predict ion for a Hund's coupling case a. The vibrational numbering was deduced fro m theoretical calculations of the interatomic potential. Six vibrational le vels have been assigned to the 5d(2)Delta and the 5d(2)Sigma, state, respec tively, allowing a determination of the Dunham coefficients in these two st ates. For the equilibrium parameters of the 5d(2)Delta state, we obtain R-e = 3.22(15) Angstrom, D-e = 900(80) cm(-1). (C) 1999 Academic Press.