Abstract: Calcium sulfide powder containing iron as an impurity was irradiated with 580, 366 or 254 nm light at 77 K. Irradiation enhanced a broad (16 G peak-to-trough) electron paramagnetic resonance (EPR) signal at g = 2.017 and caused six sharp (∼1 G) lines to appear in the X-band EPR spectrum at 347, 529, 956, 1963, 3547 and 5376 G. Enrichment of CaS with Fe2+ produced samples with similar photochemistry. It is proposed that irradiation causes the reaction Fe2+ + trap → Fe3+ + trap−, whose products give rise to six sharp EPR lines assigned to Fe3+ and a broad line associated with trap−. Both hyperfine splitting by 57Fe (13 G) and superhyperfine splitting by 33S (11.4 G) are observed in the six line spectrum. The environment of the photo-generated Fe3+ has less than octahedral symmetry. V2+ was observed at octahedral sites in unirradiated CaS for the first time, and is characterized by the EPR parameters g = 1.961 and A (hyperfine coupling) = 74.6 × 10−4 cm−1. EPR signals due to Mn2+ and Cr3+ at octahedral sites and Fe3+ at a low symmetry site were also observed in unirradiated CaS.
Publication Year: 1985
Publication Date: 1985-01-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 3
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