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HK: Hadronen und Kerne
HK 19: Application of Nuclear Techniques I
HK 19.8: Vortrag
Montag, 16. März 1998, 18:45–19:00, G
Nuclear resonance photon scattering study of the effective temperatures of diamond and of highly oriented pyrolytic graphite. — •O. Beck1, Y. Finkelstein2, R. Moreh2, D. Jäger1, U. Kneissl1, J. Margraf1, H. Maser1, and H.H. Pitz1 — 1Institut für Strahlenphysik, Universität Stuttgart, D-70569 Stuttgart — 2Physics Department, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
Nuclear resonance scattering of bremsstrahlung, employing nuclear
self-absorption from the 3089 keV and the 3684 keV levels in 13C
has been
used to determine the effective temperatures T∥ and T⊥ of
the highly oriented pyrolytic graphite (HOPG) at 10 K, 295 K,
495 K, and 683 K in
directions parallel and perpendicular to the hexagonal layers.
The effective temperature of isotopic diamond (13C) at 295 K was also
measured. The experiments were performed at the photon absorption and
scattering setup [1]
installed at the Stuttgart 4 MV Dynamitron accelerator.
In HOPG the nuclear self-absorptions for parallel and perpendicular directions
were quite different revealing a significant difference in the values
T∥ and T⊥.
Comparison between the observed values and those deduced from the vibrational
density of states of HPOG agree (within two standard deviations)
in T⊥, but the measured T∥ is about 25% higher.
A larger deviation was observed in diamond.
The results are discussed in view of the calculated phonon spectra of HOPG and
diamond.
[1] R. Moreh et al., Phys. Rev. B 56 , (1997), 187.