Vibronic intensity distribution in the B0u+-X0g+ and B1u-X1g transition of Se2

The B0u+-X0g+ and B1u-X1g transitions of 80Se2 and 78Se2 are reinvestigated. Several new bands are reported, especially for the B1u-X1g system, their vibrational numbering being confirmed by isotope shift studies. The Franck-Condon factors and r-centroid values are evaluated. By correlating the theoretically computed intensities with observed values, the internuclear distance dependence of the electronic transition moments of these two systems is determined for the first time.