Showing papers by "J. Mayers published in 1994"
TL;DR: In this article, the authors used neutron Compton scattering (NCS) measurements to determine the kinetic energies of atoms in samples of amorphous hydrogenated carbon (a-C:H), graphite and diamond at momentum transfers between 40 and 300 AA-1.
Abstract: Neutron Compton scattering (NCS) measurements have been used to determine the kinetic energies of atoms in samples of amorphous hydrogenated carbon (a-C:H), graphite and diamond at momentum transfers between 40 and 300 AA-1. We find that the kinetic energy of individual carbon atoms is the same within statistical error in a-C:H and graphite but significantly higher in diamond. The kinetic energy of the hydrogen in a-C:H is lower than expected from previous spectroscopic measurements and we infer that the sample contained molecular hydrogen. Observed deviations from the impulse approximation are consistent with theoretical calculations. We discuss future prospects for NCS measurements on non-crystalline materials.
49 citations
TL;DR: Inelastic-neutron-scattering measurements at high exchanged momentum have been performed in fluid and deviations from classical behavior have been interpreted as arising from the quantum nature of the particle oscillations in the framework of a cell model for the fluid.
Abstract: Inelastic-neutron-scattering measurements at high exchanged momentum have been performed in fluid $^{4}\mathrm{He}$ along a supercritical isochore in the 4.2--50 K temperature range. The data have been analyzed in the plane-wave impulse approximation to obtain the root-mean-square values of the particle momentum. Deviations from classical behavior have been interpreted as arising from the quantum nature of the particle oscillations in the framework of a cell model for the fluid.
24 citations
TL;DR: In this article, the atomic momentum distribution of lithium-7 in natural Li has been determined as a function of temperature from 20 to 300 K. The experiments were undertaken within the impulse approximation using the electronvolt spectrometer at ISIS.
Abstract: The atomic momentum distribution of lithium-7 in natural Li has been determined as a function of temperature from 20 to 300 K. The experiments were undertaken within the impulse approximation using the electronvolt spectrometer at ISIS. Final state effects were present above the statistical accuracy of our data and were accounted for by symmetrizing the neutron Compton profiles. The mean atomic kinetic energy of the Li nucleus was obtained directly from our measurements and was found to be approximately 10% higher than that predicted by a harmonic model incorporating a density of states derived from previous phonon measurements. A fit of the data to the Debye model gave a Debye temperature of 419+or-3 K.
24 citations