Hyperfine structure on infrared transitions of cubic sites of Pr3+ and Ho3+ ions in CaF2

Hyperfine structure is reported for sharp infrared-absorption transitions of cubic sites of Pr3+ and Ho3+ in CaF2. Cubic sites are preferentially formed in CaF2 crystals co-doped with NaF, LiF or KF. For Pr3+ and Ho3+, the hyperfine structure is observed as a simple three-line pattern for transitions between the cubic triplet ground state and upper doublet states, being the hyperfine splitting of the triplet state. Transitions between the cubic triplet ground states show complex hyperfine patterns of up to nine lines from the superposed hyperfine splitting from both the ground and upper triplets. For Ho3+, the near degenerate ground state of a triplet and doublet separated by 42 MHz yields more complex hyperfine patterns. Simulated intensity fits for the observed hyperfine patterns are presented.