  The crystal growth procedure and luminescence properties of pure and
Eu$^{2+}$-doped BaBrI and SrBrI crystals are reported. Emission and excitation
spectra were recorded under ultraviolet and vacuum ultraviolet excitations. The
energy of the first Eu$^{2+}$ 4f-5d transition and SrBrI band gap are obtained.
The electronic structure calculations were performed within GW approximation as
implemented in the Vienna Ab Initio Simulation Package. The energy between
lowest Eu$^{2+}$ 5d state and the bottom of conduction band are found based on
luminescence quenching parameters. The vacuum referred binding energy diagram
of lanthanide levels was constructed using the chemical shift model.
