Hyperfine splittings and Zeeman infrared absorption of Tb3+-doped CaF2 and SrF2

We report on the observation of pseudoquadrupole splittings of sharp infrared-absorption lines of CaF2:Tb3+. These splittings are large enough to be directly observed because the Tb3+ electronic ground levels consists of two singlets separated by only 0.18 cm(-1) for the F- C-4v center. Both the hyperfine splittings and measured Zeeman splittings for F- C-4v centers in CaF2:Tb3+ and SrF2:Tb3+ can be accounted for using wave functions derived from a previously published crystal-field analysis of experimental energy levels.