富勒烯C60中甲烷同位素溶液的低温heat capacity。同位素效应
The low temperature heat capacity of solutions of methane isotopes in fullerite C60. Isotope effects
摘要：
在1.4-120 K温度区间内，研究了间隙固溶体（CH_4）_（0.4）C_（60）的热容C（T）。分离出了CH 4分子对热容的贡献。比较了CH_4和CD_4分子对（CH_4）_0.40C_60和（CD_4）_0.40C_60溶液热容的贡献。发现在80 K以上，CH_4和CD_4分子的转动运动由平动转变为受阻转动。在14-35 K区间内，CH_4和CD_4分子的热容可以满意地用平动和平动振动以及隧道转动对核自旋平衡分布的贡献来描述。CH_4和CD_4分子热容的同位素效应主要是由于分子的局域平移振动和平动振动的频率不同。在8 K以下，CH_4和CD_4分子的隧道转动对气体热容的贡献占主导地位。这种同位素效应是由CH 4和CD 4分子的核自旋物种的转换率和转动谱的差异引起的。CH 4分子的转化率比CD 4分子的转化率低数倍。在6 K和8 K附近的CH 4和CD 4的热容曲线中观察到的弱特征分别是这些溶液的取向玻璃中的一阶相变的表现。
英文摘要：
The heat capacity C(T) of the interstitial solid solution (CH4)0.4C60 has been investigated in the temperature interval 1.4-120 K. The contribution of CH4 molecules to the heat capacity has been separated. The contributions of CH4 and CD4 molecules to the heat capacity of the solutions (CH4)0.40C60 and (CD4)0.40C60 have been compared. It is found that above 80K the character of the rotational motion of CH4 and CD4 molecules changes from libration to hindered rotation. In the interval 14-35 K the heat capacities of CH4 and CD4 molecules are satisfactorily described by contributions of the translational and libration vibrations, as well as the tunnel rotation for the equilibrium distribution of the nuclear spin species. The isotope effect in heat capacity of CH4 and CD4 molecules is due, mainly, the difference in the frequencies of local tranlational and libration vibrations of molecules CH4 and CD4. The contribution of the tunnel rotation of the CH4 and CD4 molecules to the heat capacities of this gases is dominant below 8 K. The isotopic effect is caused by the difference between both the conversion rates and the rotational spectra of the nuclear spin species of CH4 and CD4 molecules. The conversion rate of CH4 molecules is several times lower than that of CD4 ones. Weak features observed in the curves of heat capacity of CH4 and CD4 near 6 K and 8 K, respectively, are most likely a manifestation of first-order phase transitions in the orientational glasses of these solutions.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
