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

Abstract

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.

Vacuum ultraviolet silicon photomultipliers applied to BaF2 cross-luminescence detection for high-rate ultrafast timing applications

“…Notably, La doping, even at small concentrations, decreases the strength of excitation density effects, leading to more exponential decay and 'regular' component closer to the high-energy excitation value. Therefore, small concentrations of La might improve other excitation density-dependent scintillation characteristics of BaF 2 , such as yield non-proportionality with respect to gamma-ray energy (Kamenskikh et al 2020) and the response to alpha particles.…”

“…Type concentrations of La might improve other excitation density-dependent scintillation characteristics of BaF 2 , such as yield non-proportionality with respect to gamma-ray energy (Kamenskikh et al 2020) and the response to alpha particles.…”

Recent advances in time-resolved luminescence spectroscopy at MAX IV and PETRA III storage rings

“…Although, strong non-exponential decay components have been observed for various scintillators under high density excitation in the experiments at FLASH [20], which is less probable under the excitation conditions at FemtoMAX as discussed above, but creation of two core holes in the same ion is still plausible even at such excitation densities To answer this question additional studies are needed applying ultrashort excitation pulses at various excitation densities, which can be provided by modern free electron lasers. The luminescence setup at the FemtoMAX beamline has provided high quality data for the research of novel scintillation materials based on nanoplatelets as time taggers [19] and for developing an advanced model of relaxation processes in the well-known CeF3 scintillator [21].…”

Energy Structure and Luminescence of CeF3 Crystals

“…The luminescent properties of CeF 3 crystals have been the subject of numerous scientific studies since the time this material began to be considered as a promising scintillator for detectors in the field of high energy physics [ 33 , 34 , 35 ]. In this paper, among many possible aspects, we pay attention to the features of the energy structure of the crystals and the nature of the observed luminescence.…”

“…It is worth noting the positive influence of qualitative energy band schemes based on the analysis of experimental spectroscopic data [ 35 , 40 , 49 ] on the understanding of the luminescent and absorption processes in CeF 3 crystals. In particular, the concept of the formation of energy bands in CeF 3 crystals is qualitatively presented in the work [ 40 ] and is based on the combination of energy bands formed by electron energy states in the field of cerium 4f hole and 2pF 0 hole.…”