Electron spin resonance of MnS-doped KCl crystals has been investigate
d. It was found that as-grown samples show a simple spectrum looking l
ike being constructed from eighteen resonance lines. The spectrum was
very stable at room temperature and the same spectrum was also obtaine
d after annealing of quenched samples which exibit only well-known spe
ctra due to two types of Mn2+-vacancy complex centers. Such a spectrum
characteristic of as-grown samples was analysed using a model of an M
n2+-S2- complex center in an orthorhombic crystalline field basically
with principal axes along (100) cubic crystal axes: two of which are t
ilted by 100 from (100) crystal axes. When as-grown samples were coole
d down to about 150K, the tilt angle decreased to zero and the crystal
line field surrounding the center changed from orthorhombic to nearly
tetragonal. It was also found that the Mn2+-S2- complex center respons
ible for the 18-line spectra disappears by uv irradiation.