HYPERFINE-STRUCTURE OF 5I8 -] 5F5 OPTICAL-TRANSITIONS WITHIN THE TRIGONAL CENTER OF CAF2HO3+

The origin of extra hyperfine lines in two optical transitions in the I-5(8) --> F-5(5) region of the trigonal center of Ho3+ in CaF2 has be en investigated by using optically detected nuclear magnetic resonance and two-laser hole burning. Specific mixing of the excited-state hype rfine wave functions is established by the experimental measurements a nd, in a theoretical analysis, it is shown that such a mixing can aris e from the off-diagonal hyperfine interaction between adjacent E and A states. Normally forbidden transitions gain intensity from the mixing and lead to the appearance of the extra hyperfine lines in the optica l spectra. The strengths of the quadrupole, hyperfine, and off-diagona l hyperfine interaction in the ground and excited states are obtained in the analysis.