Excitons and interconfigurational transitions in CaF2:Yb2+ crystals

- We present VUV emission and excitation spectra of CaF2:Yb2+.
- Formation of free excitons leads to emission from intrinsic and extrinsic excitons.
- Temperature shifts of semiconductor band gaps apply to the intrinsic exciton peak.
- 4f14→4f135dYb2+ absorption is modeled by a semi-empirical Hamiltonian.

A time-resolved VUV spectroscopic study of emission and excitation spectra of CaF2:Yb2+ has been performed to investigate excitation and relaxation mechanisms of both impurity-trapped excitons and intrinsic excitons in CaF2. Host-to-impurity energy transfer mechanisms leading to formation of impurity-trapped excitons have been discussed. The change in free exciton excitation peak position with increasing lattice temperature has been measured and is well approximated by Viña׳s expression for the temperature shift of a semiconductor band gap. The 4f14→4f135d CaF2:Yb2+ absorption bands are successfully modeled with a semi-empirical effective Hamiltonian calculation.