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Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals
Published on: May 29, 2018
Band tail absorption saturation in CdWO4 with 100 fs laser pulses
R Laasner1, N Fedorov, R Grigonis
1Institute of Physics, University of Tartu, Tartu, Estonia. raullaasner@gmail.com
Summary
Cadmium tungstate (CdWO4) scintillators exhibit nonlinear luminescence quenching due to exciton interactions. This study reveals exciton-exciton interactions as the primary cause of scintillation nonproportionality in CdWO4.
Area of Science:
- Materials Science
- Solid State Physics
- Luminescence
Background:
- Cadmium tungstate (CdWO4) is a scintillator material used in radiation detection.
- Understanding luminescence decay kinetics is crucial for scintillator performance.
- Nonlinear quenching of luminescence affects detector accuracy.
Purpose of the Study:
- To investigate the decay kinetics of excitonic emission in CdWO4 scintillators.
- To elucidate the mechanisms behind nonlinear luminescence quenching.
- To develop a model for scintillation nonproportionality in CdWO4.
Main Methods:
- Excitation using powerful 100 fs laser pulses in the Urbach absorption region.
- Application of a high spatial and temporal resolution imaging technique.
- Development of a new model incorporating Förster interaction and absorption saturation.
Main Results:
- Observed Förster dipole-dipole interaction between self-trapped excitons.
- Discovered saturation of phonon-assisted excitonic absorption.
- Calculated an accurate Förster interaction radius of 3.7 nm.
- Identified exciton-exciton interaction as the main source of nonproportionality.
Conclusions:
- Exciton-exciton interaction is the primary cause of scintillation nonproportionality in CdWO4.
- A new quantitative model for nonproportionality has been presented.
- The findings provide a more accurate understanding of CdWO4 luminescence.
