VISIBLE AND ULTRA-VIOLET EMISSION AND ABSORPTION SPECTRA OF MGAL204-CR

Information is presented on the emission and absorption spectra at room and low temperatures of chromium activated MgAl2O4 single crystals. These crystals had been grown by a flux-melt technique, and have been shown to be structurally perfect and of high chemical purity. A systematic study of the changes in the spectra with impurity concentration has been made. The appearance of line spectra in absorption for increasing chromium concentration is described. These lines have been assigned to transitions between states of octahedral d3 predicted by crystal field theory. A discussion of their appearance, substantiated by crystallographic data, is given in terms of a modification of the selection rule by the change in the symmetry group from Oh to C3v.