Cooperative absorption transitions in LiLa1−xNdxP4O12 nanocrystals

The absorption and excitation spectra of LiLa1−xNdxP4O12 nanocrystals were studied as a function of Nd3+concentration. The relative intensities of absorption transitions increase linearly with concentration of Nd3+ ions. It was found that the absorption from the first excited term 4I11/2 significantly contributes to the absorption band intensities both at room and liquid nitrogen temperatures. The mechanism of the effect is discussed in terms of cooperative absorption transitions.