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On the interpretation of differential scattering in rare gas excitation transfer systems: He* (21 S)+Ne and Ar* (4s 3 P 2,0)+Kr, Xe J. Chem. Phys. 65, 3720 (1976); 10.1063/1.433561 Erratum: Intermolecular potentials from crossed beam differential elastic scattering measurements. I. Ne +Ar, Ne +Kr, and Ne +Xe 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 del?ths € = 0.126 kcallmole for Ne* + Ar, 0.192 kcal/mole for Kr, and 0.288 kcal/mole for Xe, with rm = 5.0 A 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 r (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 IS,2 3S). The neon 3d orbital, mixed into the excited electron's orbital by exchange repulsion, appears to playa key role in this mechanistic changeover.Relatively little is known about the interactions and 1078

Erratum: Intermolecular potentials from crossed beam differential elastic scattering measurements. I. Ne +Ar, Ne +Kr, and Ne +Xe High-resolution low-energy elastic differential cross sections have been measured for Ar-Ar over a wide angular range. Rainbow structure as well as symmetry oscillations at wide angles were resolved. These results are used to evaluate 16 different Ar-Ar potentials proposed previously and also to construct a new potential. Vibrational energy levels and the second virial coefficient calculated for the new potential are compared with experimental results.Lattice modes have been observed at 37 and 81 cm-1 in Raman spectra of orthorhombic polyoxymethylene. The normal modes of the orthorhombic polyoxymethylene crystal have been calculated and used to assign the lattice modes. The intermolecular potential has been evaluated and used to compute the dispersion curves and frequency distribution of the crystal. The calculated frequency distribution has been compared to that observed experimentally by inelastic neutron scattering.

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High-resolution differential cross sections for elastic scattering extending to wide scattering angles for He–He and Ne–Ne have been measured at two collision energies in the thermal range. The experiments were carried out by crossing two supersonic nozzle atom beams at right angles and detecting the atoms scattered in the plane of the beams with a rotatable electron-bombardment mass-filter universal detector. The results are analyzed to yield information on the interatomic potentials for these systems using a realistic and flexible potential function, and comparison is made with previously proposed potentials. For He2, a somewhat ``harder'' low-energy repulsion than that of most such potentials is inferred, while for Ne2 the potential well depth found is ∼ 30 % larger than earlier estimates and in good agreement with a preliminary spectroscopic finding.