| Autor: |
Shevtsov, Valeri, Malmi, Pekka, Ylinen, Eero, Punkkinen, Matti |
| Zdroj: |
Journal of Low Temperature Physics; Mar1999, Vol. 114 Issue 5/6, p431-444, 14p |
| Abstrakt: |
Ortho-para conversion in solid hydrogen doped with small concentration of molecular oxygen (100 and 1000 ppm) was studied by pulsed NMR in the temperature range 4.2–10.9 K. Conversion rate was mainly determined by the paramagnetic oxygen impurities. The catalyzed conversion rate constant increases with temperature in the range 4.2–8 K and becomes independent of temperature above 8 K. The high-temperature limit is 1.15(8) s−1 . The catalyzed conversion rate was shown to become temperature independent when the ortho-H2 diffusion time τd falls below the conversion time τcc in the first coordination sphere of O2 impurity. The obtained value of τcc =10.5(8) s was used to identify the position of O2 in H2 lattice as substitutional. The temperature dependence of the ortho-H2 diffusion rate near the high temperature limit was determined. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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