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Elastic and related transport cross sections for protons scattering from the noble gases He, Ne, Ar, Kr, and Xe Phys. Plasmas 13, 053501 (2006); 10.1063/1.2199808Frequency-dependent hyperpolarizabilities of the Ne, Ar, and Kr atoms using the approximate coupled cluster triples model CC3 energies of solution in N2H4 have the highest values corresponding to the smallest solubilities of the respective gases. However, !:!.So for water is by far the most negative of all the entropies of solution and so is tJi° for water. Apparently, Go does not give the correct sequence of solvents with respect to the entropy and enthalpy of solution. It is instructive to compare the magnitudes of the various terms in Eq. (1), and Table II shows the contributions for He, Ar, and SF 6 at 298. 15°K. The term RT IneRT /V 1 0) varies relatively little with the solvent, and Go is the dominant term.The results for G i are somewhat striking: ignoring the small contribution from Gi , ind, we note that N2H 4, H 2 0, N 2 H a CHa, and DMSO have nearly the same Gi.This underlines again the important role of the process of cavity formation in determining the thermodynamics of the solution process.Measurements of the velocity dependence of the total ionization cross section of argon, krypton, and xenon on impact of thermal-energy metastable neon (Ne*) atoms have been made using a velocity-selected beam of the metastable atoms. The composition (3P2j3PO ratio) of the Ne* atomic beam has been measured using an inhomogeneous-field deflecting magnet and found to be about 5/1, assuming equal detection efficiency for the two metastable species. The ionization measurements were of sufficient precision to allow simultaneous determination of both the secondary-electron-ejection efficiency and the cross section. The secondary-electron-ejection efficiency from an argon-covered gold surface on impact of metastable neon atoms was found to be 0.27±0.14. In the relative velocity range investigated (g=320-1700 m/sec) the cross section Q was found to vary as g-m below g=650 m/sec and to rise at higher relative velocities. The value of m obtained is 0.622 for Ne*-Ar, 0.728 for Ne*-Kr, and 0.874 for Ne*-Xe. A simple semiempirical model based on a two-state impact parameter treatment is used to fit the experimental results at low velocities. The model indicates that the interaction leading to ionization is short ranged.

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