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