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Hydrogen self-dynamics in liquid H-2-D-2 mixtures studied through inelastic neutron scattering

Autor(en)
Daniele Colognesi, Ubaldo Bafile, Milva Celli, Martin Neumann, Andrea Orecchini
Abstrakt

We have measured the dynamic structure factor of liquid para-hydrogen mixed with normal deuterium (T = 20 K) at two different concentration levels using incoherent inelastic neutron scattering. This choice has been made since the presence of D-2 modifies the self-dynamics of H-2 in a highly nontrivial way, acting both on its pseudophononic and its diffusive parts in a tunable way. After an accurate data reduction, recorded neutron spectra were studied through the modified Young and Koppel model and the H-2 center-of-mass self-dynamics structure factor was finally extracted for the two mixtures. Some physical quantities (i.e., self-diffusion coefficient and mean kinetic energy) were determined and compared with accurate quantum calculations, which, in addition, also provided estimates of the velocity autocorrelation function for the H-2 centers of mass. These estimates, in conjunction with the Gaussian approximation, were used to simulate the H-2 center-of-mass self-dynamics structure factor in the same range as the experimental one. The agreement between measured and calculated spectra was globally good, but some discrepancies proved the unquestionable breakdown of the Gaussian approximation in these semiquantum systems at a level comparable to that already observed in pure liquid para-hydrogen.

Organisation(en)
Computergestützte Physik und Physik der Weichen Materie
Externe Organisation(en)
Consiglio Nazionale delle Ricerche, Università degli Studi di Perugia, Institut Laue-Langevin (ILL)
Journal
Physical Review E
Band
92
Anzahl der Seiten
16
ISSN
1539-3755
DOI
https://doi.org/10.1103/PhysRevE.92.012311
Publikationsdatum
07-2015
Peer-reviewed
Ja
ÖFOS 2012
103022 Plasmaphysik, 103019 Mathematische Physik
Schlagwörter
ASJC Scopus Sachgebiete
Condensed Matter Physics, Statistical and Nonlinear Physics, Statistics and Probability
Link zum Portal
https://ucrisportal.univie.ac.at/de/publications/477f563d-d286-4711-94fa-446611299126