TY - JOUR
T1 - The use of electron scattering for studying atomic momentum distributions
T2 - The case of graphite and diamond
AU - Vos, M.
AU - Moreh, R.
AU - Tökési, K.
N1 - Funding Information:
We would like to thank Dr. J. E. Butler from the Naval Research Center in Washington DC for the CVD diamond sample used in the ECS measurements and Professor Weigold for critically reading the manuscript. This work is made possible by a grant of the Australian Research Council.
PY - 2011/7/14
Y1 - 2011/7/14
N2 - The momentum distributions of C atoms in polycrystalline diamond (produced by chemical vapor deposition) and in highly oriented pyrolitic graphite (HOPG) are studied by scattering of 40 keV electrons at 135°. By measuring the Doppler broadening of the energy of the elastically scattered electrons, we resolve a Compton profile of the motion of the C atoms. The aim of the present work is to resolve long-standing disagreements between the calculated kinetic energies of carbon atoms in HOPG and in diamond films and the measured ones, obtained both by neutron Compton scattering (NCS) and by nuclear resonance photon scattering (NRPS). The anisotropy of the momentum distribution in HOPG was measured by rotating the HOPG sample relative to the electron beam. The obtained kinetic energies for the motion component along, and perpendicular to, the graphite planes were somewhat higher than those obtained from the most recent NCS data of HOPG. Monte Carlo simulations indicate that multiple scattering adds about 2 to the obtained kinetic energies. The presence of different isotopes in carbon affects the measurement at a 1 level. After correcting for these contributions, the kinetic energies are 3-6 larger than the most recent NCS results for HOPG, but 15-25 smaller than the NRPS results. For diamond, the corrected direction-averaged kinetic energy is ≈ 6 larger than the calculated value. This compares favorably to the ≈25 discrepancy between theory and both the NCS and NRPS results for diamond.
AB - The momentum distributions of C atoms in polycrystalline diamond (produced by chemical vapor deposition) and in highly oriented pyrolitic graphite (HOPG) are studied by scattering of 40 keV electrons at 135°. By measuring the Doppler broadening of the energy of the elastically scattered electrons, we resolve a Compton profile of the motion of the C atoms. The aim of the present work is to resolve long-standing disagreements between the calculated kinetic energies of carbon atoms in HOPG and in diamond films and the measured ones, obtained both by neutron Compton scattering (NCS) and by nuclear resonance photon scattering (NRPS). The anisotropy of the momentum distribution in HOPG was measured by rotating the HOPG sample relative to the electron beam. The obtained kinetic energies for the motion component along, and perpendicular to, the graphite planes were somewhat higher than those obtained from the most recent NCS data of HOPG. Monte Carlo simulations indicate that multiple scattering adds about 2 to the obtained kinetic energies. The presence of different isotopes in carbon affects the measurement at a 1 level. After correcting for these contributions, the kinetic energies are 3-6 larger than the most recent NCS results for HOPG, but 15-25 smaller than the NRPS results. For diamond, the corrected direction-averaged kinetic energy is ≈ 6 larger than the calculated value. This compares favorably to the ≈25 discrepancy between theory and both the NCS and NRPS results for diamond.
UR - http://www.scopus.com/inward/record.url?scp=79960551138&partnerID=8YFLogxK
U2 - 10.1063/1.3607993
DO - 10.1063/1.3607993
M3 - Article
C2 - 21766954
AN - SCOPUS:79960551138
SN - 0021-9606
VL - 135
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 2
M1 - 024504
ER -