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Pulsed NMR studies in solid H2. III. Spin-lattice relaxation times

Pulsed NMR studies in solid H2. III. Spin-lattice relaxation times We report a systematic study of the longitudinal relaxation timeT 1 for solid H2 samples with ortho concentrationX between 0.15 and 0.70 and for 0.1≲T≲2 K. It is over this temperature region that substantial orientational ordering takes place, which drastically affectsT 1. The measurements were made using the solid echo technique at 9 and 27 MHz. By Fourier-transforming the echo decay, it was possible to investigate the recovery from saturation of the various parts of the NMR absorption line as a function of their distance ν−ν L from the center at the Larmor frequency ν L .The dependence ofT 1 on ν−ν L is particularly noticeable in the hcp disordered (para-orientational) phase at the lowest temperatures, where the NMR absorption is broad, and this observation is qualitatively explained. An attempt is made to understand the general features ofT 1 in the cubic ordered phase and in the hcp para-orientational phase in terms of certain relaxation mechanisms. A comparison with previous work is presented. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Low Temperature Physics Springer Journals

Pulsed NMR studies in solid H2. III. Spin-lattice relaxation times

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References (32)

Publisher
Springer Journals
Copyright
Copyright
Subject
Physics; Condensed Matter Physics; Characterization and Evaluation of Materials; Magnetism, Magnetic Materials
ISSN
0022-2291
eISSN
1573-7357
DOI
10.1007/BF00683996
Publisher site
See Article on Publisher Site

Abstract

We report a systematic study of the longitudinal relaxation timeT 1 for solid H2 samples with ortho concentrationX between 0.15 and 0.70 and for 0.1≲T≲2 K. It is over this temperature region that substantial orientational ordering takes place, which drastically affectsT 1. The measurements were made using the solid echo technique at 9 and 27 MHz. By Fourier-transforming the echo decay, it was possible to investigate the recovery from saturation of the various parts of the NMR absorption line as a function of their distance ν−ν L from the center at the Larmor frequency ν L .The dependence ofT 1 on ν−ν L is particularly noticeable in the hcp disordered (para-orientational) phase at the lowest temperatures, where the NMR absorption is broad, and this observation is qualitatively explained. An attempt is made to understand the general features ofT 1 in the cubic ordered phase and in the hcp para-orientational phase in terms of certain relaxation mechanisms. A comparison with previous work is presented.

Journal

Journal of Low Temperature Physics – Springer Journals

Published: Nov 6, 2004

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