Colour centres in YAG

Measurements of light absorption (lambda = 240 to 350 μm) of highly pure monocrystalline yttrium aluminium garnet YAG:Nd were carried out at 300 K in differential arrangement of the samples before and after irradiation with a mercury discharge tube. The energies of absorption peaks are plotted against integers n and the points fall on a straight line which fulfils the assumption that the absorption band peaks of separate color centers are given by energy levels of the harmonic oscillator Esub(n) = (n + 1/2)hν distant by hν = 0.275 eV