ELECTRON-SPIN-ECHO ENVELOPE MODULATION
ELECTRON-SPIN-ECHO ENVELOPE MODULATION
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DOI：
10.1103/physrev.137.a61
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发表时间：
1965-01-01
期刊：
影响因子：
--
通讯作者：
MIMS, WB
中科院分区：
文献类型：
--
作者：
ROWAN, LG;HAHN, EL;MIMS, WB
与固体中相邻核矩的拉莫尔周期相比，如果在磁共振微波功率脉冲下电子自旋矩在较短的时间内重新定向，则原子核在由电子自旋产生的局部偶极场中遭受非绝热变化。在脉冲后，如果核位置的电子偶极场有一个垂直于外加磁场的分量，则给定的原子核将沿一个新的量化轴进动，该量化轴与原轴明显倾斜。因此，电子位上的相干振荡核偶极场调制了核邻居较低核共振频率处的电子拉莫尔频率。影响电子自由进动信号的节拍调制的深度取决于电子-核磁耦合的大小以及微波脉冲后核量子化新轴与原轴的倾斜程度。利用双脉冲回波实验得到的电子自旋回波包络调制图，方便地测量了电子的自由进动拍。该效应的理论是在纯磁耦合核中建立的，并通过CaW o4中顺磁Ce 3+的电子自旋回波测量得到证实，其中14%丰度的w183核同位素与Ce 3+耦合。从实验中估计，电子-核配体张量偶极子-偶极子相互作用比点偶极子-偶极子相互作用大4倍，而配体超精细相互作用似乎很小。
If an electron-spin moment is reoriented by a pulse of microwave power at magnetic resonance in a time short compared to the Larmor periods of neighboring nuclear moments in a solid, the nuclei suffer non-adiabatic changes in local dipolar field produced by the electron spin. After the pulse, a given nucleus will precess about a new axis of quantization which is appreciably tilted from its original axis if the electron dipolar field at the nuclear site has an appreciable component perpendicular to an applied external magnetic field. Consequently, a coherent oscillating nuclear dipolar field at the electron site modulates the electron Larmor frequency at the lower nuclear resonance frequencies of the nuclear neighbor. The depth of the beat modulation, as it affects the electron free-precession signal, is determined by the magnitude of electron-nuclear magnetic coupling and the extent to which the new axis of nuclear quantization is tilted from its original axis after the microwave pulse. The electron free-precession beats are measured conveniently in terms of the electron-spin-echo envelope modulation pattern obtained from the two-pulse echo experiment. The theory of the effect is developed for purely magnetically coupled nuclei and is confirmed by electron-spin-echo measurements of paramagnetic Ce 3+ in CaW O 4, where the 14%-abundant W 183 nuclear isotope is coupled to Ce 3+. The electron-nuclear ligand tensor dipole-dipole interaction is estimated from experiment to be as much as four times greater than that expected from the point dipole-dipole interaction, and the ligand hyperfine interaction appears to be small.