ELECTRONIC STATES OF THE BI2 MOLECULE

The thermal emission spectrum of Bi2 in the region 3500 to 9000 cm-1 has been recorded by Fourier transform spectrometry, and laser-induced fluorescence spectra of Bi2, excited by lines of an argon-ion laser, have also been recorded. The dense thermal emission spectrum consists predominantly, if not entirely, of lines of a system al(u)(3SIGMA(u)+)-X0g+. The state al(u) is the lower state of a system observed in LIF and originally labelled E-B. Vibrational and rotational constants are derived for the states involved. Measurement of the small OMEGA-doubling in al(u) allows an estimate of the (0u--1u) separation in a 3SIGMA(u)+ to be made: it is 4540 cm-1.