Dependence Of Total Cross Section Research Articles

Hydrogen Atom Scattering: Velocity Dependence of Total Cross Section for Scattering from Rare Gases, Hydrogen, and Hydrocarbons

An apparatus for scattering experiments with thermal energy hydrogen atom beams is described. The atoms are generated by dissociation of H2 in a tungsten-tube furnace at ∼2700°K, modulated by a mechanical chopper, and velocity selected by deflection in an inhomogeneous magnetic field. After passing through a scattering chamber containing the target gas, the atoms strike a platinum strip bolometer which functions as a catalytic recombination detector (capable of detecting an H beam of ∼5×1010 atoms cm−2· sec−1). Measurements of the velocity dependence of the total collision cross section in the range 3 to 11×105 cm/sec (equivalent to 0.05 to 0.5 eV) are given for scattering of H atoms from the rare gases, H2, CH4, C2H2, C2H4, C2H6, and C(CH3)4. The results show that throughout this range attractive r−6 interactions are still predominant for Xe, C2H4, and C(CH3)4 whereas repulsive interactions are dominant for most of the other gases. The data are compared with calculations based on the Lennard-Jones (n, 6) potential and with empirical correlations of van der Waals force constants.

Atom-Atom-Streuexperimente: Geschwindigkeitsabh�ngigkeit einiger totaler Streuquerschnitte

The velocity dependence of total cross sections for the collision partners Cs-Hg, K-Hg, Xe, Kr, Ar has been measured in crossed beams. Except for Cs-Hg glory scattering oscillations were resolved. Invariably good agreement with theoretical predictions is found for the extrema velocities assumingn-6 potentials with 8≦n≦16 or exp-6 potentials with 10≦α≦18, for the amplitudes of the oscillations no fit is obtained. K-Hg, probably also K-Xe and K-Kr appear to deviate from theν−2/5 average velocity dependence expected for dipole-dipole interaction at large distances.

Alpha-particles from several elements bombarded with 30, 43 and 56 MeV protons

Several elements were bombarded with 30, 43 and 56 MeV protons from the INS(Tokyo) syncho-cyclotron. Energy spectra and angular distributions of emitted α-particles were measured by an emulsion camera. The dependence of total cross sections, angular distributions and peak energies of the spectra on the bombarding energy as well as the atomic number of target nuclei is described. The cross sections were separated into two parts, the direct process and the compound process. Energy spectra ascribed to the direct process are not inconsistent with the picture of knockout process of quasi-free α-particles.