High-resolution laser spectroscopy of YbBr.: Part II:: the A2Π ← X2Σ+ system

Absorption spectra of the A(2)Pi, <-- X(2)Sigma(+) system of YbBr have been recorded at high resolution using a single frequency cw laser arrangement. Analysis of the A-X system was challenging, owing to the high degree of spectral congestion, resulting from the small, and similar, rotational constants for both states, as well as a large number of observable isotopomers. Data for both the 0-0 and 1-0 bands of (YbBr)-Yb-174-Br-79 and (YbBr)-Yb-174-Br-81, were employed simultaneously in a least squares fit that produced estimates of the molecular parameters for the A state. Fitted B, values were used to calculate a highly accurate equilibrium bond length for the A state, R-e = 2.595406(5) Angstrom. Comparisons with the analogous A-X systems of YbF and YbCl are described. (C) 2003 Elsevier Inc. All rights reserved.