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@ARTICLE{Press:18724,
author = {Press, W. and Krasnow, I. and Zamponi, M. and Prager, M.},
title = {{R}otational {T}unneling in {CH}4 {II}: disorder effects},
journal = {The journal of chemical physics},
volume = {135},
issn = {0021-9606},
address = {Melville, NY},
publisher = {American Institute of Physics},
reportid = {PreJuSER-18724},
pages = {224509},
year = {2011},
note = {A portion of this research at Oak Ridge National
Laboratory's Spallation Neutron Source was sponsored by the
Scientific User Facilities Division, Office of Basic Energy
Sciences, U. S. Department of Energy. Also in the name of
M.P., W.P. wishes to thank the Oak Ridge National Laboratory
and the members of the BASIS team for the warm welcome and
support. One of us (WP) is thankful to the Institut fur
Experimentelle und Angewandte Physik at the University of
Kiel for financial support of the measurement at SNS. We
would like to thank A. Heidemann and K. Maki for helpful
discussions and comments.},
abstract = {Transitions within the tunneling multiplet of CH(4) in
phase II have been measured in an experiment at the
backscattering instrument BASIS of the Neutron Source SNS.
They all involve transitions from or to T-states. A
statistical model is put forward which accounts for local
departures from tetrahedral symmetry at the sites of ordered
molecules. Different from previous work, in which discrete
sets of overlap matrix elements have been studied, now large
numbers of elements as well as the ensemble of T-states are
considered. The observed neutron spectra can be explained
rather well, all based on the pocket state formalism of A.
Hüller [Phys. Rev. B 16, 1844 (1977)]. A completely new
result is the observation and simulation of transitions
between T-states, which give rise to a double peaked feature
close to the elastic position and which reflect the disorder
in the system. CH(2)D(2) molecules in the CH(4) matrix are
largely responsible for the disorder and an interesting
topic for their own sake. The simple model presented may
lend itself to a broader application.},
keywords = {J (WoSType)},
cin = {ICS-1 / JCNS (München) ; Jülich Centre for Neutron
Science JCNS (München) ; JCNS-FRM-II / JCNS-1 / JCNS-2},
ddc = {540},
cid = {I:(DE-Juel1)ICS-1-20110106 /
I:(DE-Juel1)JCNS-FRM-II-20110218 /
I:(DE-Juel1)JCNS-1-20110106 / I:(DE-Juel1)JCNS-2-20110106},
pnm = {BioSoft: Makromolekulare Systeme und biologische
Informationsverarbeitung / Großgeräte für die Forschung
mit Photonen, Neutronen und Ionen (PNI)},
pid = {G:(DE-Juel1)FUEK505 / G:(DE-Juel1)FUEK415},
experiment = {EXP:(DE-MLZ)External-20140101},
shelfmark = {Physics, Atomic, Molecular $\&$ Chemical},
typ = {PUB:(DE-HGF)16},
pubmed = {pmid:22168705},
UT = {WOS:000298250600033},
doi = {10.1063/1.3664726},
url = {https://juser.fz-juelich.de/record/18724},
}