Tl 0 , Ga 0 , and In 0 Centres in KCl Crystals

Absorption bands of In 0 and Ga 0 centres are observed in KCl : In and KCI : Ga which are related, by analogy with the corresponding bands of Tl 0 centres in KCI: Tl, to the electronic transitions 6 2 P 1/2 → 7 2 S 1/2 (the 1.80 eV band in KC1:In and 1.95 eV band in KC1:Ga) and 6 2 P 1/2 → 6 2 P 3/2 (the 0.75 eV band in KCl: In) in free In and Ga atoms. The luminescence of Tl 0 and In 0 centres at about 0.82 and 0.70 eV, respectively which may be excited in the absorption bands of Tl 0 and In 0 centres, as well as in the F band, is found and investigated. Luminescence of {In 0 + V k } pairs is detected in KCl: In and is analogous to that observed earlier in KCl: Tl.