Search

The continuum cross sections and analyzing powers from the $^{2}\mathrm{H}$, $^{3}$,4He(p\ensuremath{\rightarrow},p') and $^{3}$,4He(p\ensuremath{\rightarrow},d') reactions were measured for 98.7 and 149.3 MeV polarized protons in the angular range 17.5\ifmmode^\circ\else\textdegree\fi{} to 60\ifmmode^\circ\else\textdegree\fi{}. The $^{2}\mathrm{H}$ and $^{3}\mathrm{He}$ data show strong quasifree contributions with more ambiguous results for $^{4}\mathrm{He}$. These data are compared with distorted-wave impulse approximation calculations based on quasifree nucleon and deuteron knockout. Overall, the agreement between theory and experiment is moderately good. However, some significant discrepancies are observed and corrections to the simple model are discussed.

The scattering of beams of hydrogen molecules and helium atoms in mercury vapor has been investigated in the angular region from 5\ifmmode^\circ\else\textdegree\fi{} to 65\ifmmode^\circ\else\textdegree\fi{} at beam temperatures of 115\ifmmode^\circ\else\textdegree\fi{}, 300\ifmmode^\circ\else\textdegree\fi{} and 590\ifmmode^\circ\else\textdegree\fi{}K. The results are expressed in terms of the number of molecules scattered per incident molecule, per cm path, per ${10}^{\ensuremath{-}3}$ mm of mercury at 0\ifmmode^\circ\else\textdegree\fi{}C per unit solid angle in the direction $\ensuremath{\theta}$ to the original beam. The general shape, the absolute intensity and the change in shape of the helium scattering curves with change in beam temperature is in moderately good quantitative agreement with the quantum theory of scattering of rigid spheres as developed by Massey and Mohr. The scattering of hydrogen molecules, especially at low temperatures, shows some deviation from the results predicted by the same theory. In the case of both hydrogen and helium it is necessary to assume collision radii larger than the corresponding kinetic theory values in order to obtain the best agreement between the calculated and observed curves.

The relative yield of positive pions from H, C, Al, Cu, Ag and Pb produced by 335-Mev bremsstrahlung has been measured with a counter telescope at 5 angles to the beam line ranging from 45 deg to 150 deg and at 9 meson energies extending from 12 Mev to 125 Mev. The pion production cross sections at all angles and at all energies of 65 Mev or lower follow approximately a Z/A/sup 1/3 dependence. Fair agreement with the optical model is obtained at the lower energies, provided account is taken of effects of the Coulomb potential and the potential arising from the pion-nucleon interaction. ln the intermediate region from 22.5 to 65 Mev, the yields from the heavy nuclei are somewhat lower than predicted. At pion energies of 95 and 125 Mev, where the production cross sections follow more nearly a Z dependence, it is possible to get moderately good agreement with theory by considering the effects of the Coulomb potential on the production near the cutoff energy. (auth)

Measurements are reported of the energy required for injection of an electron into liquid argon and of the drift velocity of electrons in liquid argon at moderate field strength. It is found that the barrier to electron injection is ---0.33 eV, in moderately good agreement with a theoretical estimate of ---0.45 eV. The observed field dependence of the drift velocity is in good agreement with the recent calculations of Lekner.

An electron-spin-resonance study at room temperature has been performed on $F$ centers in LiF at hydrostatic pressures up to 4 kbar. An average value for the variation of the hyperfine constants with pressure is found to be ${a}^{\ensuremath{-}1}\frac{\ensuremath{\partial}a}{\ensuremath{\partial}P}=(2.4\ifmmode\pm\else\textpm\fi{}1.1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ ${\mathrm{bar}}^{\ensuremath{-}1}$. This result, when taken with the bulk compressibility of LiF, and the behavior with pressure of the optical transitions of $F$ centers in alkali halides, gives moderately good agreement with the point-ion model of Gourary and Adrian.