Raman heterodyne interference of inequivalent nuclear sites

A novel interference effect that is unique to the recently introduced technique of Raman heterodyne detection of NMR is illustrated for the impurity-ion crystal Pr3+: YAlO3. Experiments confirm theoretical arguments that the two inequivalent Pr nuclear sites in the host lattice generate coherent Raman signals of opposite sign that interfere. A necessary requirement, which can now be examined in detail, is that the principal nuclear quadrupole Z axis of Pr be incongruent in the ground and optically excited electronic states. © 1984 The American Physical Society.