High-Resolution Laser Spectroscopy of the A3Π1←X1Σ+ System of IBr with a Titanium:Sapphire Ring Laser

The vibrotational absorption spectra of the A←X electronic transition of I79/81Br were measured in the 11 330- to 13 220-cm−1 region using a Ti:sapphire ring laser. The P-, Q-, and R-branch lines of the rotational states from J=10 to 100 belonging to the v′←v″=(3∼20)′,←(1∼6)″ bands were assigned. The P- and R-branch lines, unlike the Q-branch lines, were split into the doublet by the nuclear quadrupole coupling effect of the I atom. The quadrupole coupling constants of eQq0 and eQq2 in the A state were estimated to be −0.030±0.018 and −0.062±0.018 cm−1, respectively, by using the first order perturbation theory. The unperturbed line positions for the rotational lines higher than J=20 were determined. The Dunham coefficients of the X state were determined by the least squares fitting method using the pseudo vibrotational transition wavenumbers obtained by calculating the combination differences between the electronic spectral lines assigned and the far infrared vibrotational lines reported by Nelander et al. (7). The spectroscopic constants of Tv′, Bv′, Dv′, and Hv′ of the A state were determined suitable for the vibrational states from v′=3 to 20 by using a least squares fitting procedure. [Copyright &y& Elsevier]