Molecular spin conversion in solid deuterated methane
Abstract
The spin conversion of methane molecules in pure deuterated methane crystals and CD4–Kr solid solution for a wide range of concentrations of krypton was investigated in the temperature range 1.5–10 K. The experiment was performed by use of a steady-state heat flow experimental setup for determination of the thermal conductivity, utilized in an unconventional way. The obtained results were discussed in the frame of the spin conversion model taking into account direct one-phonon processes and indirect librationally-activated processes. It was found that the conversion, both for pure and krypton doped crystals, is dominated by the one-phonon mechanism. However, the importance of the indirect processes increases rapidly with the temperature. The obtained results indicate that the krypton admixture does not change the values of energy levels of the spin–librational (spin–rotational)