TY - JOUR KW - pfc AU - L. Chen AU - W.-Y. Cheng AU - Jun Ye AB - We report new measurements of the hyperfine spectra of B←X transitions in the wavelength range 500–517 nm. Four effective hyperfine parameters, eqQB, CB, dB, and δB, are determined for an extensive number of rovibrational levels spanning the intermediate region 42≤v′≤70 in the electronically excited B0u+(3Πu) 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 v′=57–60, the 1g(1Πg) 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. © 2004 Optical Society of America BT - Journal of the Optical Society of America B DA - 2004-04 DO - 10.1364/JOSAB.21.000820 N1 - JILA Pub. 7169 N2 - We report new measurements of the hyperfine spectra of B←X transitions in the wavelength range 500–517 nm. Four effective hyperfine parameters, eqQB, CB, dB, and δB, are determined for an extensive number of rovibrational levels spanning the intermediate region 42≤v′≤70 in the electronically excited B0u+(3Πu) 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 v′=57–60, the 1g(1Πg) 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. © 2004 Optical Society of America PY - 2004 SE - 820-832 T2 - Journal of the Optical Society of America B TI - Hyperfine interactions and perturbation effects in the B0u+(3Πu) state of 127I2 VL - 21 ER -