The analysis of the properties of Mossbauer spectra and the conditions of preparing crystals of AgCl and NaCl doped with 5 7 C~ enabled us to suggest microscopic interpretation for five different types of chemical associations of cobalt with vacancies and oxygen and OHimpurities. A change of charge from Fe++ to Fef+f and the reverse change were observed at high temperatures.Eine Analyse der MoDbauerspektren und der Priiparationsbedingungen von AgCl und NaCl, die mit W O dotiert wurden, armoglicht, eine mikroskopische Deutung fiir. fiinf unterschiedliche Typen chemischer Assoziate von Kobalt mit Leerstellen und Sauerstoffund OH--Defekten vorzuschlagen. Eine Anderung des Ladungszustandes von Fe++ nach Fe+++ und der umgekehrte Vbergang wurden bei hohen Temperaturen beobachtet.
In the present note some disadvantages of the existing interpretation of the states of iron impurity ions in AgCl and NaCl are pointed out, and on the basis of new experiments a more adequate explanation is suggested.The investigations of AgCl/Fe using the Miissbauer effect are described in (1 to 6). in which the following velocity spectra discussed below are presented: spectrum I (isomer shift relative to iron 6 = 1.32 mm/s, quadrupole splitting 6 = 1.07 mm/s, T = 77 OK) is attributed to the association Fei 0;. The disappearance of quadrupole splitting at 300 OK is explained by the movement of a cation va- (7) is of interest here. According to (7) in the given case iron is in divalent or trivalent state, substituting Nac and is associated with cation vacancies.The samples have been prepared from AgC12) or NaCl with a content of divalent impurity cations less than lo4 mol%, molten with pure 57CoC12 in helium atmosphere. The concentration of 5' CoC12 was 10 mol%.We observed that spectrum I (AgCl) changes to spectrum 11 after annealing of the samples in the atmosphere of He with H20 at T = 400 OC during 3 h (annealingin pure O2 under the same condition does not lead to the change of spectrum I into Spec-2' -4 1) At present at the University of Sofia. 2) Crystals were received from Institut Atr Kristallphysik der Deutschen Akademie der Wissenschaften zu Berlin.
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