Abstract of Publication No. 436
Two visible luminescence bands are observed in
Re4+:Cs2ZrBr6 under NIR excitation
at temperatures between 10 and 300 K. We perform absorption,
luminescence, excitation, and time resolved spectroscopic studies at
various temperatures to characterize this upconversion luminescence
and its driving mechanism. From the time dependent measurements we
assign a ground state absorption/energy transfer upconversion type
mechanism to the upconversion process. The visible to near-infrared
photon ratio is 0.008 at T = 50 K with a laser power density
of 415 W/cm2. Most of the visible luminescence is quenched
by a strong cross-relaxation process out of the highest emitting
level as well as intense radiative interexcited state transitions.
The ReBr62- unit is one of very few transition metal
complexes with three emitting electronic levels in the near-infrared
and visible range of the electromagnetic spectrum.