Site interference in Stark-modulated photon echoes

We show that Stark-pulse-modulated photon echoes in an impurity-ion-doped crystal are generally characterized by a complex oscillatory behavior with two or more frequency components which results from the interference of the static dipole moment differences of ions located at inequivalent sites. We analyze this phenomenon using group theory and present experimental evidence for a Pr{sup 3+}- and Eu{sup 3+}-codoped YAlO{sub 3} and a Pr{sup 3+}-doped Y{sub 2}SiO{sub 5} crystal. It is demonstrated that the orientations of the dipole moments and of the crystal axes can be determined with subdegree accuracy. {copyright} {ital 1997} {ital The American Physical Society}