Electric Quadrupole Interaction and Spin Echoes in Crystals

Bloom and Norberg and also Hahn and Herzog have observed spin echoes due to electric quadrupole interaction alone and also in the presence of a weak magnetic field in addition to electric quadrupole interaction, with ${\mathrm{Cl}}^{35}$ (spin $I=\frac{3}{2}$) nuclei in NaCl${\mathrm{O}}_3$ crystal. They have explained these echoes theoretically for the particular case of $I=\frac{3}{2}$. We have calculated the spin-echo amplitudes to be expected under the above experimental conditions for nuclei of any general spin in crystals with axial symmetry. The opposite case of spin echoes in a strong magnetic field in the presence of weak electric quadrupole interaction is also discussed. The theoretical investigation leads to "slow beats" in this case also.