REINVESTIGATION OF THE CORDES BAND SYSTEM OF I2 USING A VACUUM ULTRAVIOLET-LASER

Vacuum ultraviolet (VUV) fluorescence excitation spectra of jet-cooled I2 between 195 and 168 nm were recorded using a tunable VUV "laser" generated by four-wave difference mixing in Xe gas and Hg vapor. The strongest absorption in the VUV is between the ground state and the first tier ion-pair state D0u+ (Cordes band system). Band edge wavenumbers measured in this work confirm the vibrational numbering proposed by Tellinghuisen for the VUV spectrum. D state levels between ν′ = 140 and 290 were excited and molecular constants valid between ν′ = 0 and 290 were derived. Perturbed D levels having ν′≥309 were also observed. Their band intensities appear to be related to homogeneous interactions with the e6 Rydberg state. © 1990.