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Proton energy loss spectroscopy (PELS) has been used to investigate the very high overtone states of the ν3 mode in CF4. With a new scattering apparatus, which is described here in detail, it has been possible to directly measure the energy levels of the dominantly excited ν3 mode up to its 14th overtone with an energy resolution of δE=10–15 meV, corresponding to 80–120 cm-1. The data are interpreted using the Hecht vibrational Hamiltonian which predicts the tensor splitting of the ν3 mode energy levels into sublevel bands. By adjusting the values of the anharmonicity parameters X33, G33, and T33, previously determined by IR spectroscopy and introducing a second-order anharmonicity parameter X333, it was possible to fit the ν3 mode energy levels to the measured energy loss distributions. A model based on the earlier theoretical work of Levene and Perry [H. B. Levene and D. Perry, J. Chem. Phys. 84, 4385 (1986)] for the proton–CF4 scattering process is extended to allow the simulation of complete spectra including contributions from combinations with the ν1 and ν4 mode for comparison with the experimental energy loss spectra. The influence of all relevant parameters on the simulated data is analyzed in detail. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Energy loss distributions of He+ ions after collisions with HF molecules in a secondary beam at laboratory collision energies in the range 25–50 eV show a regular structure indicating rotational excitation up to ΔJ=35 with no clear evidence for vibrational excitation. The observed propensity for large ΔJ transitions decreases with increasing collision energy but increases with increase in scattering angle. Three dimensional quasiclassical trajectory calculations using a potential energy surface based on the He+–Ne interaction at short range and a damped long range ion–dipole (quadrupole) interaction reproduce all the essential features of the experimental results. [ABSTRACT FROM AUTHOR]