Generation of (F+2)AH Centres in Sodium Ion Doped KCl:CO2-3

Abstract

Nous montrons que les centres (F+2)AH de KCl peuvent être obtenus à partir de cristaux dopés par K2CO3 et NaCl, fabriqués par la méthode de Czochralski à l'air libre. Les propriétés optiques des centres (F+2)AH ainsi produits sont exactement les mêmes que celles des centres (F+2)AH préparés par la technique habituelle, qui comporte le dopage par un superoxyde et l'emploi d'une atmosphère contrôlée

and centres in KCl and KBr doped with either carbonates or sulphates

“…A 436 nm irradiation of this sample at LNT destroys these centres and converts them to intrinsic F + 2 centres which absorb at 1378 nm. This behaviour is identical to that observed with superoxide, carbonate or nitrate doping , El Akrmi et al 1994a, Lifante et al 1991, Raerinne and Ketolainen 1993, Diaf et al 1996. However, as pointed out in the introduction, Lifante et al were unable to observe (F +…”

“…The results of Raerinne and Ketolainen (1993) not in KCl:CO 2− 3 . In a very recent paper (Diaf et al 1996), we confirm the results of Lifante et al (1991), as opposed to those of Raerinne and Ketolainen (1993): in KCl doped with either K 2 CO 3 or (K 2 CO 3 + NaCl), it is indeed possible to obtain (F +…”

“…2 ) H in KCl:SO 2− 4 and KBr:SO 2− 4 . Like in the case of KCl:CO 2− 3 (Diaf et al 1996), LNT absorption spectra of coloured KCl:SO 2− 4 after annealing and quenching show a broad band at 1440 nm, the intensity of which is enhanced by −10 • C photoaggregation with the 546 nm line. This 1440 nm band is characteristic of (F +…”

“…2 ) H and (F + 2 ) AH centres seems to depend critically on some minute details in the crystal growth procedure; indeed this problem of the sulphate doping is not the only one-there is also the question of the carbonate doping for which Raerinne and Ketolainen (1993), on one hand, and Lifante et al (1991) and Diaf et al (1996), on the other hand, arrive at opposite conclusions.…”

“…2 ) H in KBr:CO 2− 3 . The LNT absorption spectrum of CO 2− 3 -doped KBr (figure 1) displays around 290 nm an absorption band assigned to O 2− -by , a fact which suggests that decomposition of CO 2− 3 ions has occurred during additive coloration, like in the case of KCl:CO 2− 3 (Diaf et al 1996). Moreover, one already observes at this stage a weak broad band at around 1500 nm.…”