Theory of nuclear spin conversion in the β phase of solid CH4
Theory of nuclear spin conversion in the β phase of solid CH4
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固体CH4 β相核自旋转换理论
DOI：
10.1139/p80-145
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发表时间：
1980
影响因子：
1.2
通讯作者：
A. J. Berlinsky
中科院分区：
文献类型：
--
作者：
A. J. Nijman;A. J. Berlinsky
计算了部分有序β相中固体CH 4的T（I = 1）到A（I =2）自旋异构体的转化率，其机制包括分子间和分子内偶极-偶极相互作用. 在每种情况下，能量都是通过声子发射来守恒的。分子间机理导致自由转子分子的转化率为约1%/h，有序分子的转化率为约0.002至0.010%/h（0 <T <4.2）。 这里有序和无序分子转化率的差异主要是由于有序分子的T-A分裂要小得多，声子发射过程的效率与能量的立方相似。一个有序的分子与相邻的O2杂质的密切相关的计算给出大约25%/min的转换率。自由转子分子的最有效的内在机制是混合过程中，分子内偶极-偶极相互作用混合的核自旋状态和分子间的相互作用。
Calculations of the T(I = 1) to A(I = 2) spin isomer conversion rate for solid CH4 in the partially ordered β phase are performed for mechanisms involving both inter- and intramolecular dipole–dipole interactions. In each case energy is conserved by means of phonon emission. The intermolecular mechanism leads to a conversion rate of about 1%/h for the free rotor molecules and about 0.002 to 0.010%/h (for 0 < T < 4.2) for the ordered molecules. Here the difference in ordered and disordered molecule conversion rates results mainly from the fact that the T-A splitting is much smaller for ordered molecules and that the efficiency of the phonon emission process scales like the cube of this energy. The closely related calculation for an ordered molecule with a neighboring O2 impurity gives conversion rates of roughly 25%/min. The most effective intrinsic mechanism for free rotor molecules is the hybrid process in which the intramolecular dipole–dipole interaction mixes the nuclear spin states and the intermolec...