15min:

R. BRÜHL, Department of Physics, Penn State University, University Park, PA 16804; D. ZIMMERMANN, Fachbereich Physik, Technische Universität Berlin, Germany.

The rovibrational structure of the transition B²<- X² of LiAr has been investigated by means of high-resolution laser spectroscopy using a supersonic beam for production of the molecules . About 100 absorption lines could successfully be assigned for each isotopomer ⁷LiAr and ⁶LiAr providing in addition the vibrational numbering of the observed levels v=0\ldots3 of the B² state. The analysis of the experimental observations was complicated by the occurrence of perturbations between rovibrational levels of the B² and of the A² state which have not been taken into account, up to now.

For the B² interaction potential we used a Morse--van der Waals potential as an analytical expression reproducing the observed energy levels with an error margin of 0.015cm^-1. The van der Waals parameter C₆ was fixed to its theoretical value. Our preliminary results for the B² state of ⁷LiAr are R_e = 6.24(5) Å and D_e = 33.8(2.0)cm^-1.