The configuration of FA centers in Na-doped crystals was studied by means of spectroscopic measurements. The FA(Na) dipoles were found to lie along the crystal axes, and this was interpreted as being the consequence of an on-center position of Na+ ions in the lattice; in good agreement with theoretical predictions.

A.Scacco, C.Giliberti, U.M.Grassano, G.Baldacchini, N.Cremona, R.M.Montereali, A.Shpak: Radiation Effects and Defects in Solids, 1995, 134, 421-3