MOLECULAR-BEAM LASER SPECTROSCOPY OF REF - ROTATIONAL AND HYPERFINE ANALYSES OF 2 BANDS NEAR 557 NM

An extensive survey of the electronic spectrum of the ReF molecule has been carried out in the region 15 150-29 600 cm(-1) using laser-induced fluorescence spectroscopy. The ReF molecules were produced by chemical reaction in a laser-generated plasma and cooled by supersonic expansion. Both isotopomers (ReF)-Re-185-F-19(37.1%) and (ReF)-Re-187-F-19(62.9%) were studied. The observed bands are interpreted as transitions involving two different lower Omega = 0 states and a number of different excited electronic states. Using a ring dye laser, two of the bands were recorded at 100-MHz resolution, which was sufficient to resolve hyperfine structure. The analysis of these bands shows that both arise from Omega = 0 <-- Omega = 0 transitions involving a common lower state a (upsilon'') and two strongly interacting upper states b(upsilon') and c(upsilon' = 2), located at, respectively, 17 931 and 17 966 cm(-1) above a. The b(upsilon') state exhibits an avoided crossing with an unidentified state. Dispersed fluorescence studies reveal the presence of two low-lying states located at 2750 and 4240 cm(-1) above the a state. The energy difference between the two low-lying Omega = 0 states is not known; neither is it known which one is the ground state. The observed hyperfine structure is attributed to electric quadrupole effects. (C) 1994 Academic Press, Inc.