High-level ab initio calculations are performed on the coinage metal cations ͑Cu + , Ag + , and Au + ͒ interacting with each of the rare gases ͓Rg ͑Rg=He to Rn͔͒. The RCCSD͑T͒ procedure is employed, with basis sets being of approximately quintuple-quality, but with the heavier species using relativistic effective core potentials. The interaction potentials are compared to experimental and theoretical data where they exist. In addition, transport coefficients for the mobility and diffusion of the cations in the rare gases are calculated. The latter have involved a rewriting of some of the programs used, and the required modifications are discussed. The mobility results indicate that, rather than being a rare occurrence, mobility minima may be common phenomena. Finally, a new estimate is put forward for the validity of zero-field mobilities in ion mobility spectrometry.

Zero electron kinetic energy (ZEKE) spectroscopy is employed to gain information on the vibrational energy levels of the para-fluorotoluene (pFT) cation. Vibrationally resolved spectra are obtained following excitation through a range of intermediate vibrational energy levels in the S1 state. These spectra allow the observation of different cationic vibrational modes, whose assignment is achieved both from a knowledge of the S1 vibrational states and also by comparison with density functional calculations. In one notable case, clean ZEKE spectra were obtained from two overlapped S1 features. From the authors' data, the adiabatic ionization energy of pFT was derived as 70,946+/-4 cm(-1). The information on the cationic energy levels obtained will be useful in untangling the intramolecular vibrational redistribution dynamics of pFT in the S1 state.

Evidence is presented that there is a clear covalent component in the bonding of Au+ to Kr and Au+ to Xe, with some evidence that there may be such bonding between Au+ and Ar; for Au+ and Ne, there is no such evidence, and the bonding seems to be entirely physical. A model potential analysis shows that when all attractive inductive and dispersive terms out to R-8 are properly included in the Au+-Ne case, with an Ae(-bR) Born-Mayer repulsive term, essentially all the bonding in Au+-Ne can be rationalized by physical attraction alone. This is consistent with a natural bond order (NBO) analysis of the Au+-Ne ab initio wavefunctions, which shows the charge on Au+ to be very close to 1.0. In contrast, similar model potential and NBO analyses show quite clearly that physical interactions alone cannot account for the large bond energy values for the Au+-Kr and Au+-Xe complexes and are consistent with covalent contributions to the Au+-Kr and Au+-Xe interactions. Au+-Ar is seen to lie on the borderline between these two limits. In performing the model potential analyses, high-level ab initio calculations are employed [CCSD(T) energies, extrapolated to the complete basis set limit], to obtain reliable values of Re, De and omegae as input. A comparison of the gold-Xe bond distances in several solid-state Au(I, II and III) oxidation-state complex ions, containing "ligand" Xe atoms, prepared by Seppelt and co-workers, with that of the "free" Au+-Xe gas-phase ion is made, and a discussion of the trends is presented.

We employ zero-kinetic-energy (ZEKE) photoelectron spectroscopy with nanosecond laser pulses to study intramolecular vibrational redistribution (IVR) in S(1) para-fluorotoluene. The frequency resolution of the probe step is superior to that obtained in any studies on this molecule to date. We focus on the behavior of the 13(1) (C-CH(3) stretch) and 7a(1) (C-F stretch) vibrational states whose dynamics have previously received significant attention, but with contradictory results. We show conclusively that, under our experimental conditions, the 7a(1) vibrational state undergoes significantly more efficient IVR than does the 13(1) state. Indeed, under the experimental conditions used here, the 13(1) state undergoes very little IVR. These two states are especially interesting because their energies are only 36 cm(-1) apart, and the two vibrational modes have the same symmetry. We discuss the role of experimental conditions in observations of IVR in some detail, and thereby suggest explanations for the discrepancies reported to date.

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