Hyperfine interactions and perturbation effects in the B0u+(3Πu) state of 127I2

We report new measurements of the hyperfine spectra of B <-- X transitions in the wavelength range 500-517 nm. Four effective hyperfine parameters, eqQ(B), C-B, d(B), and delta(B), are determined for an extensive number of rovibrational. levels spanning the intermediate region 42 less than or equal to upsilon' less than or equal to 70 in the electronically excited B0(u)(+)((3)Pi(u)) state. Second-order perturbation accounts for most of the observed rovibrational dependence of the hyperfine interactions. In addition, it was found that, near vibrational levels upsilon' = 57-60, the 1(g)((1)Pi(g)) electronic state strongly perturbs the B state through rotational coincidence, leading to effects such as abnormal variations in the hyperfine parameters and strong u-g. mixing recorded for the transition P(84) 60-0. Various perturbation effects in the B state identified so far are summarized. Also, the radial dependence of the hyperfine interactions was examined by removal of the vibrational average in the hyperfine parameters. (C) 2004 Optical Society of America.