Sen Sabyasachi, Kaseman Derrick C, Hung Ivan, Gan Zhehong
†Division of Materials Science, University of California at Davis, One Shields Avenue, Davis, California 95616, United States.
‡Center of Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, United States.
J Phys Chem B. 2015 Apr 30;119(17):5747-53. doi: 10.1021/acs.jpcb.5b01934. Epub 2015 Apr 20.
The mechanism of (77)Se nuclear spin-lattice relaxation is investigated in binary Ge-Se glasses. The (77)Se nuclides in Se-Se-Se chain sites relax faster via dipolar coupling fluctuation compared to those in Ge-Se-Ge sites shared by GeSe4 tetrahedra that relax slower via the fluctuation of the chemical shift anisotropy. The relaxation rate for the Se-Se-Se sites decreases markedly with increasing magnetic field, whereas that for the Ge-Se-Ge sites displays no appreciable dependence on the magnetic field such that the extent of differential relaxation between the two Se environments becomes small at high fields on the order of 19.6 T. The corresponding dynamical correlation time is three orders of magnitude shorter (∼10(-9) s) for the Se-Se-Se sites, compared to that for the Ge-Se-Ge sites (∼10(-6) s). The large decoupling in the time scale between these Se environments provides direct experimental support to the commonly made assumption that the selenium chains are mechanically floppy, and the interconnected GeSe4 tetrahedra form the rigid elements in the selenide glass structure.
在二元锗 - 硒玻璃中研究了（77）硒核自旋 - 晶格弛豫机制。与通过化学位移各向异性波动弛豫较慢的、由GeSe4四面体共享的Ge - Se - Ge位点中的（77）硒核素相比，Se - Se - Se链位点中的（77）硒核素通过偶极耦合波动弛豫更快。Se - Se - Se位点的弛豫速率随磁场增加而显著降低，而Ge - Se - Ge位点的弛豫速率对磁场没有明显依赖性，使得在19.6 T左右的高场下，两种硒环境之间的弛豫差异程度变小。与Ge - Se - Ge位点（10^(-6) s）相比，Se - Se - Se位点的相应动态相关时间短三个数量级（10^(-9) s）。这些硒环境之间时间尺度上的大解耦为通常所做的假设提供了直接的实验支持，即硒链在机械上是柔软的，并且相互连接的GeSe4四面体构成了硒化物玻璃结构中的刚性元素。
