(1) Institute of Physics, Academy of Sciences of éstoniya, Riia 142, Tartu, EE2400, éstoniya;(2) Techological Center, Tartu University, Tartu, 51014, éstoniya;(3) Chemicophysical Institute, Tartu University, Tartu, 51014, éstoniya
Abstract:
Fluorescent characteristics of a series of powder CaF2: Mn phosphors (from 0.01 to 2.47 wt. % of Mn in the mixture) excited by VUV radiation with quantum energies up to 14 eV at 293 K and up to 12 eV at 85 K are measured. Narrow excitation bands of Mn2+ centers found at 7.9 and 8.6 eV (at 293 K) are assigned to partially forbidden transitions of electrons from the ground state 6S split by the crystalline field (10 Dq=0.71 eV from the literature) in two sublevels to the excited level corresponding to the 6D term of a free Mn2+ ion (3d5 → 3d44s transitions). A wide nonelementary excitation band in the region of 9.1–10.3 eV is interpreted as photogeneration of near-activator D-excitations: allowed transitions of electrons from levels that are split from the top of the valence band under the influence of an impurity ion to the free 4s-orbital of a Mn2+ ion. Channels of energy transport in the CaF2: Mn system are briefly analyzed.