Luminescence of KBr-KI Solid Solutions under X-Ray Irradiation at Liquid Helium Temperature

The luminescence of KBr crystals containing KI of various concentrations between 0 and 100 mole % under X-ray irradiation and UV illumination has been investigated at liquid helium temperature. The two characteristic emission bands are observed at about 3.50 eV and 4.30 eV. The former band at 3.50 eV is shown to originate from the recombination of an electron with the self-trapped hole of the complex V k -center, IBr - and π-polarized with a degree of polarization P =-0.15±0.03. From the excitation spectra for this band by UV illumination, a possibility of energy transfer between excited Br - ions and I - ions is discussed. The latter band at 4.30 eV is due to a cluster of I - ions.