Ortho-para conversion in solid hydrogen, catalyzed by molecular oxygen impurities

Journal Article · Thu Aug 01 04:00:00 EDT 1996 · Journal of Low Temperature Physics

DOI:https://doi.org/10.1007/BF00754095· OSTI ID:441429

Shevtsov, V; Scherbakov, A ^[1]; Malmi, P; Ylinen, E; Punkkinen, M ^[2]

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1. Kurchatov Institute, Moscow (Russian Federation)
2. Univ. of Turku (Finland)

Ortho-para conversion in solid hydrogen with small amounts of molecular oxygen as impurity (0.01-0.5%) was studied by NMR in the temperature range 4.2-7 K. The observed conversion rate was substantially greater than that of the natural conversion process in pure solid H{sub 2} and revealed a strong dependence on temperature and the oxygen content in the sample. Obviously, the conversion is catalyzed by the large paramagnetic moments of O{sub 2} impurities. Since the influence of O{sub 2} is of very short range, the overall rate of the catalyzed conversion in the sample is determined by the relative diffusion of ortho-H{sub 2} and O{sub 2} impurities. The diffusion coefficient was found to obey an Arrhenius behavior D(T) = 3(2) {center_dot} 10{sup {minus}11} {center_dot} exp[96(8)/T] cm{sup 2} s{sup {minus}1}. This temperature dependence is interpreted in terms of vacancy-particle exchange by quantum tunneling through the intervening barrier.

• Sponsoring Organization: USDOE
• OSTI ID: 441429
• Journal Information: Journal of Low Temperature Physics, Journal Name: Journal of Low Temperature Physics Journal Issue: 3-4 Vol. 104; ISSN JLTPAC; ISSN 0022-2291
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
CATALYTIC EFFECTS
HYDROGEN
OXYGEN
SOLIDS
SPIN FLIP
TEMPERATURE RANGE 0000-0013 K