Electronic states of the Bi2 molecule

Abstract The thermal emission spectrum of Bi 2 in the region 3500 to 9000 cm −1 has been recorded by Fourier transform spectrometry, and laser-induced fluorescence spectra of Bi 2 , 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 a1 u ( 3 Σ + u )-XO + g . The state a1 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 Ω-doubling in al u allows an estimate of the (O − u -1 u ) separation in a 3 Σ + u to be made: it is 4540 cm −1 .