An optical spectral hole-burning technique has been used in study of the hyperfine and nuclear quadrupole interactions of ${}_{}{}^{243}{}_{}{}^{}\mathrm{Am}_{}^{3+}{}_{}{}^{}$ in ${\mathrm{CaWO}}_4$. Previous work on ${}_{}{}^{243}{}_{}{}^{}\mathrm{Am}_{}^{3+}{}_{}{}^{}$ in ${\mathrm{LaCl}}_3$ [Phys. Rev. B 53, 2385 (1996)] provided an analysis of the nuclear quadrupole interaction in the ${}_{}{}^7{}_{}{}^{}\mathrm{F}_0^{}{}_{}{}^{}$ ground state and predicted an anomalous nuclear quadrupole interaction in the optically excited state ${}_{}{}^5{}_{}{}^{}\mathrm{D}_1^{}{}_{}{}^{}$. In the present work on ${}_{}{}^{243}{}_{}{}^{}\mathrm{Am}_{}^{3+}{}_{}{}^{}$ doped into ${\mathrm{CaWO}}_4$, hyperfine energy levels in both the ${}_{}{}^7{}_{}{}^{}\mathrm{F}_0^{}{}_{}{}^{}$ ground state and the ${}_{}{}^5{}_{}{}^{}\mathrm{D}_1^{}{}_{}{}^{}$ excited state of an ${}_{}{}^{243}{}_{}{}^{}\mathrm{Am}_{}^{3+}{}_{}{}^{}$ ion have been resolved in spectral hole-burning experiments. A theoretical analysis is reported for the hyperfine and nuclear quadrupole interactions in the non-Kramers doublet of the ${}_{}{}^5{}_{}{}^{}\mathrm{D}_1^{}{}_{}{}^{}$ excited state of ${}_{}{}^{243}{}_{}{}^{}\mathrm{Am}_{}^{3+}{}_{}{}^{}$ in ${\mathrm{CaWO}}_4$. Whereas the crystal-field antishielding effect dominates the ground state nuclear quadrupole splitting, a first order electronic hyperfine interaction dominates the excited state splitting. It is shown that the contribution from the nuclear electric quadrupole interactions in the ${}_{}{}^5{}_{}{}^{}\mathrm{D}_1^{}{}_{}{}^{}$ excited state is much smaller than that in the ${}_{}{}^7{}_{}{}^{}\mathrm{F}_0^{}{}_{}{}^{}$ ground state, because the first order nuclear quadrupole interaction with the 5f electrons is canceled in part by the contribution from the lattice interaction.

• Received 18 November 1996

DOI:https://doi.org/10.1103/PhysRevB.55.8967