High-resolution laser spectroscopy of LiAr:: Spectroscopic parameters and interaction potentials of the A 2Π and the B 2Σ states

The absorption spectrum of the LiAr molecule has been recorded with high resolution using a supersonic beam and applying the method of laser-induced fluorescence. Altogether, about 1400 absorption lines due to the transitions A (2)Pi <--X (2)Sigma and B (2)Sigma <--X (2)Sigma of the two isotopomers (LiAr)-Li-7-Ar-40 and (LiAr)-Li-6-Ar-40 could successfully be assigned. The spectroscopic parameters of vibration and rotation, of spin-orbit splitting, and of lambda -type doubling have been obtained for vibrational levels 5-10 of A (2)Pi and 0-3 of B (2)Sigma. Using the observed rovibrational energies as input data the interatomic potentials of both electronic states have been determined in form of analytical functions by means of a fully quantum-mechanical method of approach. For the equilibrium values we get R-e=2.50(8) Angstrom, D-e=957(30) cm(-1) for A (2)Pi and R-e=6.24(5) Angstrom, D-e=33.8(1.0) cm(-1) for B (2)Sigma. (C) 2001 American Institute of Physics.