Abstract of Publication No. 561
Low-temperature absorption spectra of single crystals of Tm2+-doped
CsCaCl3, CsCaBr3, and CsCaI3 in the spectral
range from 8700 to 47000 cm–1 are presented. Weak
sharp-line 4f-4f absorptions around 8800 cm–1 are
essentially independent of the nature of the halide. More-intense broad
absorptions cover the region between 12000 and 47000 cm–1.
They are assigned to 4f-5d excitations and interpreted in terms of a simple
qualitative picture taking into account the most important interactions. As a
result of two counterbalancing effects, the onsets of the 4f-5d spectra are
almost coincident in the three materials: The blue-shift of about 3000
cm–1 between chloride and iodide resulting from the
decreasing crystal field splitting of 5d is roughly balanced by the red-shift
resulting from the reduced energy gap between the average energy of the
4f13 and the 4f125d1 electron configurations.
The absorption helps the understanding of the most unusual light emission
properties of these materials.