Coherent Raman spectroscopy of nuclear quadrupole resonance of La around Pr^<3+> in LaF_3

Coherent Raman spectroscopy was applied for an optical-rf double-resonance study of a LaF_3 crystal doped with Pr^. The coherent nuclear spin Raman scattering was detected as a function of the applied rf frequency. Exciting the resonance condition of the ^3H_4→^3P_0 transition of Pr^ (20 925 cm^), only the La nuclei surrounding the Pr^ ion were observed through their nuclear quadrupole resonance ~NQR!. The double resonance between the optical transition of the ion and the NQR transition of its neighboring nucleus is theoretically described by analyzing the magnetic dipolar interaction that is affected by the optical excitation. Under a certain restriction, which the present system fulfills, the intensity of the Raman heterodyne signal can be described by an analytical function of the internuclear vector and the orientation of the electric-field gradient ~EFG! at the Pr and La nuclei. Five different neighboring La nuclei were observed. They are different from the bulk La in both magnitude and orientation of the EFG. In addition, it was found that the laser frequency jitter affects the relative signal intensity of the different La NQR transitions through the optical pumping of the La spin levels.[S0163-1829(98)03145-2