Luminescence of photochromic centers in calcium fluoride crystals doped with Lu3+ ions

• We found luminescence attributed to photochromic centers (PC(Lu)) centers in CaF2.
• Excited states of PC(Lu) centers are formed by admixture orbitals of Lu and F-center.
• Ground state of PC(Lu) center is slightly disturbed 1s level of F′-center.

We report data on the luminescence spectra associated with photochromic centers in X-ray irradiated calcium fluoride crystals doped with Lu ions. Irradiation in low energy photochromic centers absorption band excites emission, which can be identify with transitions into photochromic centers. Ab initio calculation of absorption spectrum of photochromic center agrees rather well with experimental data.