Knight shift, spin-lattice relaxation and electric field gradient in technetium metal
Knight shift, spin-lattice relaxation and electric field gradient in technetium metal
复制标题
锝金属中的奈特位移、自旋晶格弛豫和电场梯度
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
K. Guerman
中科院分区：
文献类型：
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作者：
V. Tarasov;Y. Muravlev;K. Guerman
用脉冲99Tc核磁共振在120 ~ 400 K的温度范围内，在7.04 T的磁场下测量了金属锝的自旋晶格弛豫时间（T1）、各向同性Knight位移（Kiso）和四极耦合常数（CQ）。结果发现（T1×T）-1 = 3.21±0.35 (s K)-1, Kiso(T) = 7305-1.52T ppm；四极耦合常数CQ = 5.74±0.05 MHz与温度无关。从接触、d极化和轨道超精细相互作用的角度分析了T1和Kiso的实验数据。结果表明，接触相互作用对弛豫速率的贡献最大，而奈特位移受轨道相互作用的支配。99Tc核位的电场梯度被认为是不同符号的电子能级和晶格能级贡献的总和。计算得到的晶格贡献是正的，约占电子贡献的30%。所得的qel和qat值与其他具有六边形密排晶格的金属的数据进行了比较。
Spin-lattice relaxation time (T1), isotropic Knight shift (Kiso) and quadrupole coupling constant (CQ) have been measured in technetium metal by pulsed 99Tc NMR in a magnetic field of 7.04 T in the temperature range 120-400 K. It was found that (T1×T)-1 = 3.21±0.35 (s K)-1, Kiso(T) = 7305-1.52T ppm; the quadrupole coupling constant CQ = 5.74±0.05 MHz is temperature independent. Experimental data on T1 and Kiso are analysed in terms of the contact, d-polarization and orbital hyperfine interactions. It is shown that the main contribution to the relaxation rate comes from the contact interaction and the Knight shift is governed by the orbital interaction. The electric field gradient at the 99Tc nucleus site is considered to be a sum of the electron qel and lattice qlat contributions with different signs. The calculated lattice contribution is positive and constitutes about 30% of the electronic contribution. The obtained values of qel and qlat are compared with data for other metals with hexagonal close-packed lattices.