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Bochum 1998 – wissenschaftliches Programm

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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. Pitz11Institut 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.

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