Luminescence of Pure and Cu-Doped Alkali Halide Single Crystals

In order to understand some x-ray excited emission bands in pure alkali halides, crystals were doped with the corresponding copper halides. It has been found that a band, which is also often present in "pure" or thermally treated alkali halides, is due to a Cu center. The excitation spectrum of the Cu impurity at room temperature has also been measured. It is shown that the radiative transitions connected with Cu centers involve electrons.