Ortho-para conversion in solid hydrogen, catalyzed by molecular oxygen impurities
- Kurchatov Institute, Moscow (Russian Federation)
- 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, Vol. 104, Issue 3-4; Other Information: PBD: Aug 1996
- Country of Publication:
- United States
- Language:
- English
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