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Title: Anomalous ortho-para conversion of solid hydrogen in constrained geometries

Abstract

Using cw NMR techniques, we have measured the ortho-para conversion of solid hydrogen constrained to the interior of the molecular cages of zeolite. The conversion observed in the constrained geometry is very different from that of bulk solid hydrogen. Two distinct conversion rates were observed for short and long times. An apparently bimolecular conversion rate of 0.43% h{sup {minus}1} (one-fourth of the bulk value) dominates during the first 500 h, and the rate then {ital increases} to 2.2% h{sup {minus}1}. The initial slow rate is explained in terms of a reduced number of nearest neighbors and possible wall effects, and the fast rate is attributed to the formation of small ortho-H{sub 2} Rclusters at later times. Surface effects due to magnetic impurities do not appear to determine the conversion rate in the samples studied.

Authors:
; ;  [1]
  1. Department of Physics, University of Florida, Gainesville, Florida (USA)
Publication Date:
OSTI Identifier:
6133650
Resource Type:
Journal Article
Journal Name:
Physical Review, B: Condensed Matter; (United States)
Additional Journal Information:
Journal Volume: 44:18; Journal ID: ISSN 0163-1829
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; HYDROGEN; PHASE TRANSFORMATIONS; MOLECULAR CRYSTALS; DIFFUSION; NUCLEAR MAGNETIC RESONANCE; ORIENTATION; WALL EFFECTS; ZEOLITES; CRYSTALS; ELEMENTS; INORGANIC ION EXCHANGERS; ION EXCHANGE MATERIALS; MAGNETIC RESONANCE; MATERIALS; MINERALS; NONMETALS; RESONANCE; SILICATE MINERALS; 665100* - Nuclear Techniques in Condensed Matter Physics - (1992-)

Citation Formats

Rall, M, Brison, J P, and Sullivan, N S. Anomalous ortho-para conversion of solid hydrogen in constrained geometries. United States: N. p., 1991. Web. doi:10.1103/PhysRevB.44.9932.
Rall, M, Brison, J P, & Sullivan, N S. Anomalous ortho-para conversion of solid hydrogen in constrained geometries. United States. https://doi.org/10.1103/PhysRevB.44.9932
Rall, M, Brison, J P, and Sullivan, N S. Fri . "Anomalous ortho-para conversion of solid hydrogen in constrained geometries". United States. https://doi.org/10.1103/PhysRevB.44.9932.
@article{osti_6133650,
title = {Anomalous ortho-para conversion of solid hydrogen in constrained geometries},
author = {Rall, M and Brison, J P and Sullivan, N S},
abstractNote = {Using cw NMR techniques, we have measured the ortho-para conversion of solid hydrogen constrained to the interior of the molecular cages of zeolite. The conversion observed in the constrained geometry is very different from that of bulk solid hydrogen. Two distinct conversion rates were observed for short and long times. An apparently bimolecular conversion rate of 0.43% h{sup {minus}1} (one-fourth of the bulk value) dominates during the first 500 h, and the rate then {ital increases} to 2.2% h{sup {minus}1}. The initial slow rate is explained in terms of a reduced number of nearest neighbors and possible wall effects, and the fast rate is attributed to the formation of small ortho-H{sub 2} Rclusters at later times. Surface effects due to magnetic impurities do not appear to determine the conversion rate in the samples studied.},
doi = {10.1103/PhysRevB.44.9932},
url = {https://www.osti.gov/biblio/6133650}, journal = {Physical Review, B: Condensed Matter; (United States)},
issn = {0163-1829},
number = ,
volume = 44:18,
place = {United States},
year = {1991},
month = {11}
}