The sizable ground-state nuclear polarization which accompanies the optical pumping of the $^{3}H_{4}\ensuremath{-}^{1}D_{2}$ (16 872-${\mathrm{cm}}^{\ensuremath{-}1}$) $\ensuremath{\sigma}$ transition of
Pr3+ in La
F3 was utilized to observe enhanced and saturated absorptions within the inhomogeneously broadened spectral line. The observed hyperfine splittings of the lowest
1D2 state are 3.7 and 4.7 MHz at 2.0\ifmmode^\circ\else\textdegree\fi{}K. These splittings were fitted by a spin Hamiltonian $\mathcal{H}=D[{I}_{z}^{2}\ensuremath{-}\frac{I(I+1)}{3}]+(\frac{E}{2})({I}_{+}^{2}+{I}_{\ensuremath{-}}^{2})$, where $D=\ensuremath{-}1.10\ifmmode\pm\else\textpm\fi{}0.05$ and $E=\ensuremath{-}0.48\ifmmode\pm\else\textpm\fi{}0.05$ MHz. The observed linewidths (including the exciting laser linewidth) were 0.8 MHz. The deconvoluted optical transition linewidths (full widths at half-maximum) are 0.20\ifmmode\pm\else\textpm\fi{}0.05 MHz.