Density of states in solid deuterium: Inelastic neutron scattering study

• Published in: Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2009-08, Vol.80 (6), Article 064301
• Main Authors: Frei, A., Gutsmiedl, E., Morkel, C., Müller, A. R., Paul, S., Urban, M., Schober, H., Rols, S., Unruh, T., Hölzel, M.
• Format: Article
• Language: English
• Subjects: COLD NEUTRONS; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DENSITY; DEUTERIUM; EXCITATION; FRM-II REACTOR; GADOLINIUM OXIDES; HCP LATTICES; HYDROGEN; INELASTIC SCATTERING; MOLECULES; NEUTRON DIFFRACTION; PHONONS; ROTATIONAL STATES; SOLIDS; THERMAL NEUTRONS; TIME-OF-FLIGHT METHOD
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.80.064301

The dynamics of solid deuterium (sD{sub 2}) is studied by means of inelastic scattering (coherent and incoherent) of thermal and cold neutrons at different temperatures and para-ortho ratios. In this paper, the results for the generalized density of states (GDOS) are presented and discussed. The measurements were performed at the thermal neutron time-of-flight (TOF) instrument IN4 at ILL Grenoble and at the cold neutron TOF instrument TOFTOF at FRM II Garching. The GDOS comprises besides the hcp phonon excitations of the sD{sub 2} the rotational transitions J=0{yields}1 and J=1{yields}2. The intensities of these rotational excitations depend strongly on the ortho-D{sub 2} molecule concentration c{sub o} in sD{sub 2}. Above E=10 meV there are still strong excitations, which very likely may originate from higher-energy damped optical phonons and multiphonon contributions. A method for separating the one-phonon and multiphonon contributions to the density of states will be presented and discussed.