Ar Cross Sections Research Articles

Solar neutrino-induced reactions

The 8B solar neutrino-induced 37Cl(ν e, e −) 37 Ar cross section is obtained using weak matrix elements from a recent model calculation to complement existing experimental data: ω 8 B model=(1.27 ± 0.01) x 10 −42 cm 2. More generally, constraints that can be placed on this cross section by a model-independent analysis are considered and yield ω 8 B model=(1.27 ± 0.23) x 10 −42 cm 2.

Inversion of total cross sections for repulsive ion-atom scattering in the classical regime II

A previously derived formula for inversion of incomplete total scattering cross sections into ion-atomic potentials is generalized to take into account total cross sections measured as a function of both ion energy and aperture. The formula allows an estimate of the error of the potential determined. Analysis of K +-Ar cross sections of Sielanko and coworkers shows that measurements of this are especially valuable not only because of the easy extension of the range in which the potential is determined, but mainly because of the decrease of the error.

Inversion of total cross sections for repulsive ion-atom scattering in the classical regime

With the use of the momentum approximation of classical scattering theory we derive an inversion formula for incomplete total scattering cross sections measured by ion-atom scattering experiments as a function of ion energy. The formula allows direct determination of repulsive interatomic potential functions without the use of trial functions for the potential and, in addition, an estimate of the absolute error as a function of interatomic distance. Analysis of the K +Ar cross sections of Amdur and coworkers shows that for the inversion to be only moderately accurate, the experimental data must cover an energy range of more than an order of magnitude.

Elastic Differential Scattering ofHe+Ions by Ne and Ar and ofAr+Ions by Ar in the 10-600-eV Range

Absolute elastic differential scattering cross sections of ${\mathrm{He}}^{+}$ on Ne and Ar and of ${\mathrm{Ar}}^{+}$ on Ar have been measured at relative energies ranging from 10 to 600 eV and scattering angles of 1\ifmmode^\circ\else\textdegree\fi{} to 40\ifmmode^\circ\else\textdegree\fi{}. The ${\mathrm{He}}^{+}$ on Ne and Ar cross sections are monotonically decreasing functions of angle and have a superimposed ripple structure which is attributed to curve-crossing effects. No rainbow-angle structure is evident on these curves. The ${\mathrm{Ar}}^{+}$-on-Ar cross sections indicate both rainbow scattering and oscillations associated with symmetric charge exchange. From the values of the rainbow scattering angle, the estimated binding energy of $\mathrm{Ar}_{2}^{}{}_{}{}^{+}$ is 1.6\ifmmode\pm\else\textpm\fi{}0.3 eV, assuming the general shape of the attractive potential resembles that of $\mathrm{He}_{2}^{}{}_{}{}^{+}$.

Lyman Alpha Production in Proton-Rare Gas Collisions

Cross sections for Lyman alpha radiation production in proton reactions at 1 to 25 kev with Ne, He, Xe, Ar, and Kr were measured. Two prominent maxima were observed in the Ar, Kr, and Ne reaction cross sections while the He(p) cross section has a maximum with a shoulder on its highenergy side. The cross section for the Xe(p) has a 10-kev peak and gives indication of another at very low proton energy. (D.C.W.)