# Optical and structural properties of $\mathrm{Eu^{2+}}$ doped BaBrI and BaClI crystals

## TL;DR

This study investigates the optical, structural, and electronic properties of Eu²⁺ doped BaBrI and BaClI crystals, highlighting their potential as scintillators for radiation detection through experimental and theoretical analyses.

## Contribution

It provides new crystallography data, spectroscopic measurements, and electronic band structure calculations for Eu²⁺ doped BaBrI and BaClI crystals, advancing understanding of their scintillation properties.

## Key findings

- Determined the energies of Eu²⁺ 4f-5d transitions.
- Measured the band gaps of BaBrI and BaClI crystals.
- Predicted the Eu²⁺ energy levels relative to the valence band.

## Abstract

The work is necessitated by search for new materials to detect ionizing radiation. The rare-earth ions doped with ternary alkali earth-halide systems are promising scintillators showing high efficiency and energy resolution. Some aspects of crystal growth and data on the structural and luminescence properties of BaBrI and BaClI doped with low concentrations of $\mathrm{Eu^{2+}}$ ions are reported. The crystals are grown by the vertical Bridgman method in sealed quartz ampoule. New crystallography data for BaClI single crystal obtained by single crystal X-ray diffraction method are presented in this paper. Emission, excitation and optical absorption spectra as well as luminescence decay kinetics are studied under excitation by X-ray, vacuum ultraviolet and ultraviolet radiation. The energies of the first 4f-5d transition in $\mathrm{Eu^{2+}}$ and band gap of the crystals have been obtained. We have calculated the electronic band structure of the crystals using density functional theory as implemented in the \latin{Ab Initio}. Calculated band gap energies are in accord with the experimental estimates. The energy of gaps between the occupied Eu$^{2+}$ 4f level and the valence band top are predicted. In addition, positions of lanthanide energy levels in relation to valence band have been constructed using the chemical shift model.