The absorption, excitation, and luminescence spectra of MgAl2O4:Co2+ a
re studied. The spectra are measured at temperatures from 4.2 to 300 K
. From the low temperature absorption spectra the Racah parameters and
energy level assignments are derived. Three emission bands are found,
one in the visible and two in the infrared region. The visible one is
assigned to the 4T1(4P) --> 4A2 transition. In the infrared the 4T1(4
P) --> 4T2 and 4T1(4P) --> 4T1(4F) transitions are observed. It is sho
wn that the luminescence originates from different Co2+ sites situated
in a weak ligand field. The luminescence decay curves are measured in
a wide range of temperatures (from 4.2 to 300 K) and found to be non-
exponential. The temperature dependence of luminescence and the mechan
ism of non-radiative deactivation of the 4T1(4P) level is briefly disc
ussed.