Emission Spectra of Silicate Phosphors with Manganese Activation

It is shown that the emission spectra of manganese activated zinc orthosilicate, zinc beryllium silicate and calcium silicate can be expressed as the sum of several Gaussian distribution curves. The observed distributions for zinc orthosilicate and for calcium silicate can be fully given as the sum of three bands, while that of zinc beryllium silicate requires five bands. In general, only the amplitude of the bands is affected by changes in composition with their location and sharpness remaining unchanged. Based on the hypothesis that transitions between energy levels of manganese ions in the crystal lattice are responsible for the emission of visible light, tentative assignments are given for the transitions responsible for each observed bands. The geometry of the crystal lattice is shown to influence the location of the bands as exemplified by the difference between zinc silicate and calcium silicate. Modifying ions, such as beryllium, are shown not to affect the band locations though they cause the development of new bands not previously observed in the unmodified phosphor. A hypothesis for this appearance of new bands is proposed in terms of a change in electron spin.