10min:

TOKIO YUKIYA, NOBUO NISHIMIYA, MASAO SUZUKI, Department of Electronics and Information Technology, Tokyo Polytechnic University, Iiyama 1583, Atsugi City, Kanagawa 243-0297, Japan; ROBERT J. LE ROY, Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.

Bromine dimer has been studied by many researchers in various wavelength regions. The A ³ _1u and X ^{1 +}_g states have been well observed using magnetic rotation spectroscopy, by laser-induced fluorescence,^, by laser absorption, by Fourier transform absorption, and by UV emission.~ This yields a data set consisting of 16916 transitions in which the observed vibrational levels for the X ^{1 +}_g and A ³ _1u states span 83% and 99% of the potential well depths, respectively, with the highest observed vibrational level of the A ³ _1u state lying only 2 cm^-1 below the dissociation limit.^a In order to provide the most compact and comprehensive description of these data, and the ability to make reliable predictions outside their range, we have chosen to perform a ``direct potential fit'' (DPF), rather than a conventional Dunham-expansion analysis. In particular, accurate analytic potential energy functions for the A ³ _1u and X ^{1 +}_g states are determined from a combined-isotopologue DPF analysis that also yields the electronic isotope shift, the -doubling radial strength function, and an experimental value for the long-range inverse-power C₅ constant of the A ³ _1u state, as well as centrifugal Born-Oppenheimer Breakdown (BOB) functions for both states. To reveal characteristics of the A ³ _1u state, band constants calculated from these potentials are compared with those determined from a conventional parameter-fitting analysis reported by Coxon.