arXiv subjects

Roman Shendrik

Publications and source records attributed to Roman Shendrik.

5 recordsLinked to original sources

arXiv2024

Ultrafast core-to-core luminescence in BaF$_2$-LaF$_3$ single crystals

This study investigates the mechanisms underlying ultrafast cross-luminescence observed in BaF$_2$ crystals doped with LaF$_3$. We identified an ultrafast luminescent component with a decay time of approximately 150 ps, which emerges under excitation energies exceeding 24 eV as a novel radiative recombination process between electrons in the 5p core band of Ba2+ and holes in the 5p core band of La$^{3+}$. Ab initio calculations support this hypothesis, showing that the energy levels of the core bands facilitate such transitions. The findings indicate that BaF$_2$-LaF$_3$ scintillators hold significant promise for applications in time-of-flight tomography.

cond-mat.mtrl-sci↗

arXiv2018

Role of electron and hole centers in energy transfer in BaBrI crystals

In this paper we study a role of F-centers, hole centers and excitons in energy transfer in Eu-doped BaBrI crystals. Optical absorption spectra, thermally stimulated (TSL) and photostimulated (PSL) luminescence in wide temperature range 7-300 K are studied in undoped and doped with different concentrations of Eu ions BaBrI crystals. Based on experimental and calculated results two possible energy transfer processes from host to Eu$^{2+}$ ions are established.

cond-mat.mtrl-sci↗

arXiv2015

Luminescence of photochromic centers in calcium fluoride crystals doped with Lu$^{3+}$ ions

We report data on the luminescence spectra associated with photochromic centers in X-ray irradiated calcium fluoride crystals doped with Lu ions. Irradiation in low energy photochromic centers absorption band excites emission, which can be identify with transitions into photochromic centers. Ab initio calculation of absorption spectrum of photochromic center agrees rather well with experimental data.

cond-mat.mtrl-sci↗

arXiv2013

Luminescence of cadmium fluoride doped with rare-earth ions

Absorption, excitation and emission spectra of cadmium fluoride crystals doped with rare-earth ions were investigated. In contrast to alkaline-earth fluorides the absorption spectra due to 4f - 5d transitions of Ce$^{3+}$, Pr$^{3+}$ and Tb$^{3+}$ ions are broadened. No 5d-4f emissions were observed. These prove that 5d(e$_g$) levels of rare earth ions lie in conduction band of CdF$_2$ crystal. Emission spectra of Tb$^{3+}$ show the group of 4f-4f $^5$D$_4$-$^7$F$_j$ lines in contrast to other alkaline-earth fluorides where emission due to $^5$D$_3$-$^7$F$_j$ transitions is also observed. The absence of the emission is due to position of $^5$D$_3$ level within condution band. Among the all measured crystals doped with impurity ions (Pr, Nd, Eu, Ho, Tb, Tm, Yb, Ga, In or Mn), the CdF$_2$ doped with Pr$^{3+}$, Tb$^{3+}$, or Mn$^{2+}$ ions have the highest light outputs under x-ray excitation.

cond-mat.mtrl-sci↗

arXiv2013

Absolute light yield measurements on SrF$_{2}$ and BaF$_{2}$ doped with rare earth ions

Results of absolute light output measurements on strontium and barium fluoride doped with PrF$_3$ and CeF$_3$ are presented and compared with scintillators having well-known light output (NaI-Tl, CsI-Tl, BGO). For pure SrF$_2$ crystal we obtain a value of about 28600 photons/MeV.

cond-mat.mtrl-sci↗