Electron spin relaxation times T1 and Tm of Tb3+ and Tm3+ in 1:1 water:ethanol and of Tb3+ doped (2%) in crystalline La2(oxalate)3 decahydrate were measured between about 4.2 and 10 K. Both cations are non-Kramers ions and have J = 6 ground states. Echo-detected spectra are compared with CW spectra and with field-stepped direct-detected EPR spectra. Due to the strong temperature dependence of T1, measurements were not made above 10 K. Between about 4.2 and 6 K T1 is strongly concentration dependent between 1 and ~ 50 mM. T1 values at 4.2 K are in the µs range which is orders of magnitude faster than for 3d transition metals. Phase memory times, Tm, are less than 500 ns, which is short relative to values observed for 3d transition metals and organic radicals at 4 K. Tm is longer in the oxalate lattice which is attributed to the lower proton concentration in oxalate than in the organic solvent, which decreases nuclear spin diffusion. The rigidity of the crystalline lattice also may contribute to longer Tm.

中文翻译：

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Tb3+ 和 Tm3+ 离子的电子自旋弛豫

Tb3+ 和 Tm3+ 在 1:1 水：乙醇中的电子自旋弛豫时间 T1 和 Tm，以及掺杂在晶体 La2（草酸盐）3 十水合物中的 Tb3+ (2%) 的电子自旋弛豫时间 T1 和 Tm 在大约 4.2 和 10 K 之间测量。两种阳离子都是非 Kramers 离子并且有 J = 6 个基态。将回波检测到的光谱与 CW 光谱和场步进直接检测到的 EPR 光谱进行比较。由于 T1 对温度有很强的依赖性，因此没有在 10 K 以上进行测量。在大约 4.2 和 6 K 之间，T1 在 1 和 ~ 50 mM 之间强烈依赖于浓度。4.2 K 时的 T1 值在 µs 范围内，比 3d 过渡金属快几个数量级。相记忆时间 Tm 小于 500 ns，相对于在 4 K 时观察到的 3d 过渡金属和有机自由基的值而言是短的。草酸盐晶格中的 Tm 较长，这是由于草酸盐中的质子浓度低于有机溶剂中的质子浓度，从而降低了核自旋扩散。晶格的刚性也可能有助于延长 Tm。