Intensity of laser-excited fluorescence of erbium ethylsulfate

The fluorescence spectrum for the 4S 3 2 → 4I 15 2 transition of the erbium ethylsulfate crystal has been observed at 87 K by using the 488.0 nm line of an Ar+ laser. According to the Judd—Ofelt theory for spectral intensity, the relative intensities of 10 σ transitions and 5π transitions between the manifolds have been evaluated using wavefunctions obtained from a crystalfield calculation including configuration interaction. The calculated intensities are in fair agreement with experiment. A discussion is given of the approximations employed.