G. C. Summerfield

Neutron Scattering in Normal and Deuterated Polyethylene

The one‐ and two‐phonon amplitude‐weighted directional frequency functions are calculated for normal and deuterated crystalline polyethylene. These results are compared to previously measured frequency spectra for stretch‐oriented normal polyethylene and to new measurements on deuterated polyethylene. In addition, the Debye‐Waller factors are calculated for oriented polyethylene and compared with elastic‐scattering data.

Multiple scattering in small-angle neutron scattering measurements on polymers☆

Abstract Multiple scattering corrections in small-angle neutron scattering experiments on polymers have been examined. Numerical calculations show that, for typical experimental conditions, the second-order scattering is less than 2% of the first-order scattering for QR g up to 10.0. An approximate expression is also given for obtaining a rough estimate of the second-order scattering without numerical calculation.

Quasiclassical equation of motion for spins

Abstract We discuss the difficulties of using quasiclassical methods to describe two time correlation functions for spin systems. We show that there is an inherent difficulty in deriving quasiclassical equations of motion. In particular, we show that for the two spin case the equivalents of the Heisenberg operators S∼j(t) satisfy equations which deviate dramatically from what one would expect for classical equations.

Time dependence of neutron pulses in the slowing down energy region

Abstract We examine the neutron flux in the slowing down region following a pulse of neutrons of speed vo. We show that the flux is a function of the product vt and the ratio v/vc. We further show that for finite moderators the dependence upon the ratio v/vo is of the form (v/vo)μM where μM depends upon the non-leakage probability.

Inelastic Neutron Scattering by Gaseous O2

The magnetic contributions to neutron diffraction by molecular oxygen have been studied both experimentally and theoretically. We extend the theoretical studies by performing a calculation of the magnetic interaction in the inelastic neutron cross section for gaseous O2. The magnetic inelastic cross section for O2 is significantly different from the nuclear inelastic cross section due to the lack of spherical symmetry in the magnetic‐moment distribution about each oxygen nucleus. It is expected from these results that the inelastic cross section for O2 will provide more information about the magnetic‐moment distribution than the angular distribution. We present representative calculations to indicate the size and nature of the magnetic contribution to the inelastic cross section.