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arXiv 1008.4032cond-mat.soft
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固态乙醇结晶态和玻璃态的低温电子自旋弛豫

Low temperature electron-spin relaxation in the crystalline and glassy states of solid ethanol

Marina Kveder, Dalibor Merunka, Milan Jokić, Boris Rakvin

摘要:

用X波段电子顺磁共振(EPR)谱研究了氮氧自由基自旋探针在乙醇玻璃和结晶乙醇中的光谱性质。在两个主机矩阵的不同的各向异性的分子包装证明了不同的刚性极限值的最大超精细分裂的自旋探针的信号。与乙醇玻璃相比,溶解在结晶乙醇中的自旋探针的相记忆时间显著缩短,从光谱扩散的贡献方面进行了讨论。低频动力学的影响表现在温度的依赖性和在不同的光谱位置测量的数据之间的差异。这一现象是在慢运动各向同性扩散模型的框架内解决的[S. Lee和S. Z. Tang,Phys.Rev.B31,1308(1985)],预测在极低温度下毫秒范围内的自旋探针动力学。自旋探针在乙醇玻璃中的自旋-晶格弛豫时间较短,这是由于玻色子峰激发增强了玻璃基质中自旋系统与晶格之间的能量交换。

英文摘要:

X-band electron paramagnetic resonance (EPR) spectroscopy was used to study the spectral properties of a nitroxide spin probe in ethanol glass and crystalline ethanol, at 5 - 11.5 K. The different anisotropy of molecular packing in the two host matrices was evidenced by different rigid limit values for maximal hyperfine splitting in the signal of the spin probe. The significantly shorter phase memory time, , for the spin probe dissolved in crystalline ethanol, as compared to ethanol glass, was discussed in terms of contribution from spectral diffusion. The effect of low-frequency dynamics was manifested in the temperature dependence of and in the difference between the data measured at different spectral positions. This phenomenon was addressed within the framework of the slow-motional isotropic diffusion model [S. Lee, and S. Z. Tang, Phys. Rev. B 31, 1308 (1985)] predicting the spin probe dynamics within the millisecond range, at very low temperatures. The shorter spin-lattice relaxation time of the spin probe in ethanol glass was interpreted in terms of enhanced energy exchange between the spin system and the lattice in the glass matrix due to boson peak excitations.

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