HIGH-RESOLUTION LASER EXCITATION SPECTROSCOPY OF THE A(1)SIGMA(+)-X(1)SIGMA(+) TRANSITION OF BAS

The high-resolution laser excitation spectrum of the A(1) Sigma(+)-X(1) Sigma(+) transition of BaS was recorded. The BaS molecule was prepared by a gas-phase reaction of Ba metal vapor with CS2 in a Broida oven. The 2-0, 3-0, 4-0, 5-0, 5-1, 6-1, 7-1, 7-2, 8-2, 9-2, and 8-3 vibrational bands were rotationally analyzed. Approximately 600 lines !for the main isotopomer (BaS)-Ba-138-S-32 (67.5%) were measured and fitted to yield spectroscopic constants for the A(1) Sigma(+) and X(1) Sigma(+) states. The A(1) Sigma(+) state is found to be extensively perturbed by two low-lying electronic states, the A'(II)-I-1. and a(3)II(i). (C) 1995 Academic Press. Inc.