INVESTIGATION OF NUCLEAR SPIN CONVERSION OF METHANE IN SOLID HYDROGEN
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Date
2001
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Ohio State University
Abstract
We have studied nuclear spin conversion of $CH_{4}$ and $CD_{4}$ trapped in solid $H_{2}$ and solid $D_{2}$ by Fourier-transform infrared spectroscopy. It has been shown that the rotational quantum number J of methane is still a good quantum number in solid hydrogen. The effective rotational constant has been found to be about 90% of the gas phase value. The vibration-rotation absorption of both $CH_{4}$ and $CD_{4}$ exhibited time-dependent intensity changes at liquid He temperatures. These changes are interpreted to be a result of the $I = 1 \rightarrow I = 2$ nuclear spin conversion which accompanies the $J = 1 \rightarrow J = 0$ rotational relaxation. The conversion rate is on the order of $10^{-3} min^{-1}$, but the rate depends on the temperature of the crystal. Mechanisms of the nuclear spin conversion in solid hydrogen will be discussed.
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Author Institution: Division of Chemistry, Graduate School of Science, Kyoto University; Division of Chemistry, Graduate School of Science, Kyoto University