Luminescence Studies in Ca(PO3)2:Eu3+Glass by Laser-Induced Fluorescence Line-Narrowing Technique. I. Optical Transition Mechanism of the5D0-7F0Line

Fluorescence spectra have been measured in Ca(PO 3 ) 2 :Eu 3+ at 77 K under dye laser excitation at various energies within the absorption lines due to the transitions 7 F 0 , 7 F 1 - 5 D 0 , 5 D 1 . It has been found that the 5 D 0 - 7 F 0 transition probability and the mean energy of the three 5 D 0 - 7 F 1 lines are linearly correlated with the energy of the 5 D 0 - 7 F 0 line, and also that this energy is quadratically correlated with the transition energy between 5 D 0 and the lowest level of 7 F 1 . These results are interpreted in terms that the spreads of these energies and the transition probability are due to the site-to-site variation in the second-order crystal-field parameter. Further, the forbidden 5 D 0 - 7 F 0 transition is concluded to be allowed by the borrowing of the intensity from the 5 D 0 - 7 F 2 ( M J =0) line through the J -mixing. Using polarization characteristics of fluorescence, whether the lines are due to the electric or magnetic dipole transition is determined and the Stark levels of the 7 F 1 and 5 D 1 manifolds are assigned. It is also shown that the point symmetry of the Eu 3+ site is C 2 V or C 2 .