Rotational analysis of the A-X band system of Bi2

Laser excitation spectra of the A-X system of Bi 2 have been measured, individual rotational transitions being excited. Absolute wavenumbers of rotational lines were determined by a wavemeter and frequency marks of a Fabry-Pérot interferometer with an accuracy better than 0.001 cm −1 . Including eleven vibronic bands in the rotational analysis, we determined the rotational structure of the A-X band system.