This paper investigates the ESR spectra of ZnS:Mn

Cu and ZnS:Cu and their dependence on doing

annealing and ageing of samples. ESR Spectra and Concentration QuenchingThe line shape of ESR spectra of ZnS:Mn

Cu powder samples changes with increasing Mn

2+

ion concentration. When the Mn

2+

ion concentration is as low as 0.1% (g/g)

the spectra of isolated Mn

2+

ions have six hyperfine lines. As Mn

2+

ion concentration grows larger than 0.3% (g/g)

the six hyperfine lines gradually merge into an envelope. At a high concentration as 1.5% (g/g)

spectrum appears as a structureless single line with a narrower half-width. It has been suggested that the formation of Mn

2+

pairs and clusters and hence the exchange-coupling ion are the cause of line enveloping and its width narrowing.