Anomalous ortho-para conversion of solid hydrogen in constrained geometries

Journal Article · Fri Nov 01 00:00:00 EST 1991 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.44.9932· OSTI ID:6133650

Rall, M; Brison, J P; Sullivan, N S ^[1]

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1. Department of Physics, University of Florida, Gainesville, Florida (USA)

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.

• OSTI ID: 6133650
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 44:18; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

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-)