CERN Accelerating science

Preprint
Report number	E14-2001-171 ; JINR-E14-2001-171
Title	Influence of Concentration and Temperature on Tunneling and Rotational Dynamics of Ammonium in $Rb_{1-x}(NH_{4})_{x}$ Mixed Crystals
Author(s)	Natkaniec, I ; Dianoux, A J ; Martínez-Sarrion, M L ; Mestres, L ; Herraiz, M ; Smirnov, L S ; Shuvalov, L A
Affiliation	(Frank Laboratory of Neutron Physics, Dubna) ; (H.Niewodniczanski Institute of Nuclear Physics, 31-342 Krakow, Poland) ; (Institute Laue-Langevin, 156X, 38042 Grenoble Cedex, France) ; (Inorganic Chemistry Department, University of Barcelona, Spain) ; (SSC RF Institute of Theoretical and Experimental Physics, 4117259 Moscow, Russia) ; (Institute of Crystallography RAS, 117333 Moscow, Russia)
Publication	2001
Imprint	13 Aug 2001
Number of pages	11
Subject category	Condensed Matter
Abstract	The Rb_{1-x}(NH_{4})_{x} mixed crystals are studied by inelastic incoherent neutron scattering using time-of-flight spectrometers in the concentration region of the x-T phase diagram 0.01\lq x \lq 0.66 at 5\lq T \lq 150 K, where dynamic and static orientational disorder phases are generally found. It is shown that at 5 K rotational tunneling levels for ammonium concentrations x=0.01,0.02 and 0.06 are similar. Additional tunneling levels are observed for x=0.16 which can be explained as the result of T-states splitting for annount of NH_{4}-NH_{4} interaction. Tunneling levels are not observed for 0.40 as the result of forming orientational glass state. The elastic incoherent structure factors for concentrations 0.01\lq x \lq 0.16 (dynamic orientational disordered \alpha-phase), x=0.40 (orientational glass state) and 0.50\lq x \lq 0.66 (orientational ordered state) have different temperature dependences.
Submitted by	[email protected]