1. Max-Planck-Institut fur Physik komplexer Systeme, 38 Noethnitzer Str., Dresden D-01187, Germany
2. B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Nauky Ave., Kharkiv 61103, Ukraine
3. Institute for Scintillation Materials, STC “Institute for Single Crystals” of the National Academy of Sciences of Ukraine, 60 Nauky Ave., Kharkiv 61001, Ukraine