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1H NMR Study of Molecular Motions and Phase Transitions in Methyl Ammonium Hexabromo Selenate [(CH3NH3)2SeBr6]

Murthy, BVS and Ramesh, KP and Ramakrishna, J (1993) 1H NMR Study of Molecular Motions and Phase Transitions in Methyl Ammonium Hexabromo Selenate [(CH3NH3)2SeBr6]. In: Berichte der Bunsen-Gesellschaft für Physikalische Chemie, 97 (4). pp. 603-607.

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Official URL: http://onlinelibrary.wiley.com/doi/10.1002/bbpc.19...

Abstract

The temperature dependence of 1H spin-lattice relaxation time, T1, and that of the second moment, M2, are analysed in the temperature range 390 K to 77 K. A plot of T1 vs inverse temperature shows three phase transitions at 250 K, 167 K and 111 K. At 167 K, T1 displays a large jump while it shows changes in slope at 250 K and 111 K. In the high temperature phase (> 167 K), the correlated motion of CH3 and NH3 groups is found to cause the relaxation while their uncorrelated motion takes over in the low temperature phases (< 167 K). The unusual T1 behaviour in phase II (250 K-167 K) is ascribed to the small angle torsion of the cation. A constant M2 value of ∼ 9.7 G2, throughout the range of temperature studied, indicates the presence of reorientation of CH3 and NH3 groups.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to John Wiley and Sons.
Keywords: Methyl Ammonium Hexabromo Selenate;Phase Transitions;Proton Magnetic Relaxation;Second Moment;Spectroscopy, Nuclear Magnetic Resonance.
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 10 Feb 2011 09:33
Last Modified: 10 Feb 2011 09:33
URI: http://eprints.iisc.ernet.in/id/eprint/35483

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