Heteronuclear rare-gas dimer bonding: Understanding the nature of the Rydberg states that dissociate to the highest energy level of the Xe-*(5d) manifold

(1+1(')) resonance enhanced multiphoton ionization (REMPI) spectra of jet-c ooled KrXe and ArXe in the vicinity of the high energy Xe*5d[3/2](1)(0)<-- Xe(S-1(0)) atomic line at 83889.99 cm(-1) were obtained by exciting the neu tral dimers with tunable coherent vacuum ultraviolet (VUV) radiation genera ted by four-wave sum mixing in mercury vapor, and then detecting the result ant ions in a time-of-flight (TOF) mass spectrometer. Precise excited state constants were derived from analyses of the resultant vibrational fine str ucture, while equilibrium bond lengths were estimated from Franck-Condon fa ctor intensity simulations. Excited state symmetries were deduced from sepa rate ultraviolet (UV) (2+1) REMPI spectra recorded with linearly and circul arly polarized light. The results of this work confirm a recent model propo sed by Lipson and Field, where the RgXe*(5d) states are predicted to be str ongly destabilized relative to RgXe*(6p) due to strong 5d-6p Xe* l-mixing i nduced by the ground state Rg atom partner making up the dimer. Orbital mix ing is also responsible for the observation of appreciably strong RgXe(*)(5 d) spectra in both one- and two-photon excitation. (C) 1999 American Instit ute of Physics. [S0021-9606(99)00231-7].