Anomalous ortho-para conversion of solid hydrogen in constrained geometries

Journal Article · Fri Nov 01 04:00:00 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), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 44:18; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

665100* -- Nuclear Techniques in Condensed Matter Physics -- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CRYSTALS
DIFFUSION
ELEMENTS
HYDROGEN
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MAGNETIC RESONANCE
MATERIALS
MINERALS
MOLECULAR CRYSTALS
NONMETALS
NUCLEAR MAGNETIC RESONANCE
ORIENTATION
PHASE TRANSFORMATIONS
RESONANCE
SILICATE MINERALS
WALL EFFECTS
ZEOLITES