Neutron scattering studies of methyl derivatives of benzene selected as potential materials for cold neutron moderators
Natkaniec I.1,2, Hołderna-Natkaniec K.3, Kalus J.4
- 1Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna 141980, Russian Federation
- 2H. Niewodniczanski Institute of Nuclear Physics, 31-342 Krakow, Poland
- 3Institute of Physics, A. Mickiewicz University, 61-614 Poznan, Poland
- 4Institute of Physics, University of Bayreuth, D-95440 Bayreuth, Germany
Physica B: Condensed Matter, 350, pp.e651-e653, 2004
DOI:: 10.1016/j.physb.2004.03.174
Abstract:
Vibrational spectra of toluene, m- and p-xylenes and mesitylene, measured by inelastic incoherent neutron scattering at 20 K, are compared. Internal barriers for methyl rotation in free molecules of these compounds are quite low. External barriers caused by crystal packing significantly increase the frequencies of methyl librations in solid p-xylene and the low temperature phase III of mesitylene. The vibrational spectra of glassy states of mesitylene in solution with toluene and m-xylene indicate relatively low barriers for methyl librations and, typical for disordered solids, additional density of states at low frequencies, which makes these materials preferable as potential moderators for cold neutron sources. © 2004 Elsevier B.V. All rights reserved.
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