The electronic and nuclear magnetic moments and the effective nuclear-quadrupole interactions of the ground and excited states of the 2940.97- D21H43 transition of Pr3+ ions in tetragonal sites of CaF2 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 gh=5.44 MHz/G and g=0. The nuclear magnetic splitting factor parallel to the C4 axis is g2=1.65 kHz/G, and the effective quadrupole coupling constant Dg=+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 Pr141, i.e., 4.2754(5)N. For fields parallel to the C4 axis, e is unenhanced: e2=1.29240.0001 kHz/G. However, e2=2.120.05 kHz/G shows modest enhancement due to second-order admixture of other D21 electronic levels. This result is used to assign the symmetry of the excited state as A1 in the point group C4v, and to locate the E level 200 cm-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 De=-0.44 MHz. © 1984 The American Physical Society.