Concentration dependence of absorption spectra of Pr3+ in LaF3

The effect of active center concentration on absorption spectra of Pr3+ in LaF3 (3%, 5%, 7%) was investigated in the temperature range 5–300 K. It was found that the spectra were strongly dependent on concentration. The intensity of the 3P0 line significantly decreased with increasing Pr3+ concentration. An anomalous temperature dependence of band intensities of 3P0, 3P1 and 3P2 terms was observed. The nature of concentration dependent electronic transitions is discussed briefly.