Hyperfine structure and nuclear and electronic Zeeman effect of theD21↔H43transition ofPr3+:CaF2

Abstract

The electronic and nuclear magnetic moments and the effective nuclear-quadrupole interactions of the ground and excited states of the 2940.97-\AA{} $^{1}D_{2}\ensuremath{\leftrightarrow}^{3}H_{4}$ transition of ${\mathrm{Pr}}^{3+}$ ions in tetragonal sites of Ca${\mathrm{F}}_{2}$ have been measured using spectral hole burning, rf- and microwave-optical double-resonance and laser-excited fluorescence-excitation spectroscopy. The ground state is an electronic doublet of $E$ symmetry whose electronic magnetic moment tensor is given by $\frac{{g}_{\ensuremath{\parallel}}\ensuremath{\beta}}{h}=5.44$ MHz/G and ${g}_{\ensuremath{\perp}}=0$. The nuclear magnetic splitting factor parallel to the ${C}_{4}$ axis is $\frac{{\ensuremath{\gamma}}_{\ensuremath{\parallel}}^{g}}{2\ensuremath{\pi}}=1.65$ kHz/G, and the effective quadrupole coupling constant ${D}^{g}=+1.39$ MHz is dominated by pseudoquadrupole effects. The excited state is an electronic singlet, and rf-optical double resonance was used to determine the nuclear Zeeman splittings and obtain a very precise value for the nuclear magnetic moment of $^{141}\mathrm{Pr}$, i.e., $4.2754(5){\ensuremath{\mu}}_{N}$. For fields parallel to the ${C}_{4}$ axis, ${\ensuremath{\gamma}}^{e}$ is unenhanced: $\frac{{\ensuremath{\gamma}}_{\ensuremath{\parallel}}^{e}}{2\ensuremath{\pi}}=1.2924\ifmmode\pm\else\textpm\fi{}0.0001$ kHz/G. However, $\frac{{\ensuremath{\gamma}}_{\ensuremath{\perp}}^{e}}{2\ensuremath{\pi}}=2.12\ifmmode\pm\else\textpm\fi{}0.05$ kHz/G shows modest enhancement due to second-order admixture of other $^{1}D_{2}$ electronic levels. This result is used to assign the symmetry of the excited state as ${A}_{1}$ in the point group ${C}_{4v}$, and to locate the $E \mathrm{level}\ensuremath{\sim}200$ ${\mathrm{cm}}^{\ensuremath{-}1}$ higher. Unlike that of the ground state, the excited-state quadrupole coupling is dominated by real electric quadrupole interactions, and the constant is determined to be ${D}^{e}=\ensuremath{-}0.44$ MHz.