Band tail absorption saturation in CdWO4 with 100 fs laser pulses

Decay Kinetics of Gd3Al2Ga3O12:Ce3+ Luminescence under Dense Laser Irradiation

The decay kinetics of Gd₃Al₂Ga₃O₁₂:Ce³⁺ single crystal luminescence were studied under dense laser excitation. It was shown that the decay times as well as the intensity of Ce³⁺ luminescence depend on the excitation density. The observed effects were ascribed to the interaction between excitons as well as to the features of energy transfer from the excitons to Ce³⁺. The numerical simulation of the experimental results was performed for justification of the proposed model.

Decay Kinetics of CeF3 under VUV and X-ray Synchrotron Radiation

Characteristic dimensions and evolution times of regions of secondary electronic excitations created by the interaction of ionizing radiation with matter cannot be measured directly. At the same time these are essential parameters both for engineering of nanostructured composite materials defining optimal layer thickness and nanoparticles radii and for the development of optimized scintillators. The paper demonstrates how such spatial and temporal data can be extracted from luminescence decay kinetics excited by vacuum ultraviolet (VUV) and X-ray photons at modern sources of synchrotron radiation MAX IV and PETRA III. Specific features of energy-band structure of self-activated crystal CeF3 are discussed, and its potential for a super-fast detection of ionizing radiation evaluated. Diffusion-controlled dipole–dipole interaction of Frenkel excitons is demonstrated to account well for the luminescence non-exponential decay kinetics providing information on the scales of excited regions created by photons of different energy. For 20 eV photons the radius of excited regions is estimated to be 10 nm, and for 200 eV photons it increases to 18 nm. Effective radius of excited regions of complicated shape created by 19 keV is as large as 80 nm and the diffusion length of Frenkel excitons over radiative time is 14 nm.

Cation influence on exciton localization in homologue scheelites

Homologue scheelite crystals CaWO4, SrWO4, and BaWO4 possess similar crystal and electronic structure, but their luminescence exhibits drastically different thermal stabilities. By measuring the temperature dependence of the decay time of the intrinsic luminescence and fitting it to a three level model, we have qualitatively shown the effective exciton radius to increase in the order CaWO4 → SrWO4 → BaWO4, which explains the differences in the thermal stability. The origin of the variation in the exciton radii is suggested to be related to differences in the excited state dynamics in these crystals. From the decay kinetics measured under conditions of high excitation density, the efficiency of dipole-dipole interaction between excitons is shown to grow with exciton delocalization.

G0W0 band structure of CdWO4

The full quasiparticle band structure of CdWO4 is calculated within the single-shot GW (G0W0) approximation using maximally localized Wannier functions, which allows one to assess the validity of the commonly used scissor operator. Calculations are performed using the Godby-Needs plasmon pole model and the accurate contour deformation technique. It is shown that while the two methods yield identical band gap energies, the low-lying states are given inaccurately by the plasmon pole model. We report a band gap energy of 4.94 eV, including spin-orbit interaction at the DFT-LDA (density functional theory-local density approximation) level. Quasiparticle renormalization in CdWO4 is shown to be correlated with localization distance. Electron and hole effective masses are calculated at the DFT and G0W0 levels.