Differential elastic scattering of Ne*(3s 3P2,0) by Ar, Kr, and Xe: Optical potentials and their orbital interpretation

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Abstract
Optical potentials for the title systems have been derived by simultaneous fitting of thermal‐energy elastic scattering angular distributions reported here and ionization cross section and quenching rate constant data from other laboratories. The real parts of these potentials are similar to sodium–rare gas van der Waals potentials, with well depths ε=0.126 kcal/mole for Ne*+Ar, 0.192 kcal/mole for Kr, and 0.288 kcal/mole for Xe, with rm=5.0 Å for all three systems. A direct inversion of Ne*+Xe rainbow scattering yields a potential in good accord with the parametric form used in fitting. One‐electron model potential calculations also produce curves in good agreement with experiment, and shed light on the effect of orbital mixing (hybridization of the Ne*3s orbital) on the shape of the repulsive branch of the potentials. The derived resonance widths Γ (imaginary parts of the optical potentials) give evidence that a Coulomb or radiative mechanism dominates the thermal‐energy quenching by Penning ionization, in contrast to the exchange mechanism thought to be dominant for He*(2 1S,2 3S). The neon 3d orbital, mixed into the excited electron’s orbital by exchange repulsion, appears to play a key role in this mechanistic changeover.