Spectroscopic properties of (F₂⁺)_AHcentres in oxygen- and sulphur-doped alkali halides

Abstract

In search of potential laser-active colour centres, we have created and spectroscopically studied for the first time (F2+)AH centres in KCl:Li+:O2- and RbCl:Na+:O2-. We compare them with the 'classical' (F2+)AH centres in KCl:Na+:O2- and KBr:Na+:O2-. We describe preparation procedures, and absorption and emission spectra at 100 and 5 K. We study the stability of the centres in the dark at room temperature, an important property for laser applications. Preliminary data concerning (F2+)AH centres in KBr:Na+:S2- are also reported.

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

“…Photoaggregation with the 546 nm line of mercury at −10 • C leads to a considerable increase of this band which peaks at 1510 nm. In agreement with data obtained with other dopants , El Akrmi et al 1994a, we assign this band to the (a) variety of (F +…”

“…2 ) H centres in the dark at room temperature shows the same behaviour as that reported by El Akrmi et al (1994a) for the same centres in crystals doped with the superoxide KO 2 .…”

“…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 +…”

“…(F + 2 ) AH in KBr:CO 2− 3 :Na + . Like in the case of KCl:CO 2− 3 :Na + , the LNT absorption spectrum of KBr:CO 2− 3 :Na + after photoaggregation shows a broad infrared band (here located at around 1390 nm), in addition to the 285 nm UV band, which is assigned to O 2− --Na + complexes by El Akrmi (1994). In agreement with the results from this reference, LNT irradiation with the 436 nm or even the 365 nm mercury line shifts the infrared band to 1578 nm.…”

“…2 ) H centres , El Akrmi et al 1994a. Thermal stability is much higher in NaCl:OH − , NaCl:S 2− , and NaCl:Se 2− than in all other crystals (El Akrmi et al 1994a).…”