Mass-resolved VUV laser spectroscopy of XeAr: Two competing predissociation pathways in the C1 state

Mass-resolved excitation spectra of the C1 – X0 band of XeAr were measured under jet-cooled conditions using a tunable coherent vacuum ultraviolet ~VUV! light (l;130 nm) as an excitation light source and a high-resolution (m/Dm;1100) reflectron time-of-flight mass spectrometer. The rotational structure of the C1 – X0 (v8,0) (v852 – 6) vibronic bands were recorded by monitoring the parent XeAr ions and the fragment Xe ions. From the analysis of the rotational structures, the existence of the two dissociation pathways from the C1 state was identified for the first time; i.e., ~i! the rotationally dependent predissociation caused by an electron-rotation interaction ~Land/or S-uncoupling! with the dissociative state with 0 symmetry correlating with the Xe 6s8(1/2)0 level, and ~ii! the rotationally independent predissociation caused by the electrostatic interaction with a repulsive state with V51 symmetry correlated either with the Xe 6s(3/2)1 level or the Xe 6s(3/2)2 level. From the least-squares fit to the partially resolved rotational structures, the dissociation rates for these two pathways as well as the band origins and the rotational constants, were derived for the v852 – 6 levels in the C1 state. © 1998 American Institute of Physics. @S0021-9606~98!01513-X#