Eu III identification and Eu abundance in CP stars

We report the first identification of the Eu III lambda 6666.347 line in op tical spectra of CP stars. This line is clearly present in the spectra of H R 4816, 73 Dra, HR 7575, beta CrB, and alpha(2) CVn, while it is marginally present or absent in spectra of the roAp stars (rapidly oscillating Ap sta rs, cf. Kurtz 1990) alpha Cir, gamma Equ, HD 203932, GZ Lib (33 Lib), and H D 24712. Careful synthetic spectrum calculations for the Eu rr lambda 6645.11 Line t aking into account hyperfine, isotopic, and magnetic splittings allow us to obtain more accurate Eu abundances in the atmospheres of 9 CP stars. In mo st cases the derived abundances are significantly lower than the previous r esults reported for some of the stars based on coarse analysis of the famou s blue Eu II Lines. Assuming an ionization balance in the stellar atmospher es we give an estimate of the astrophysical oscillator strength log(gf)=1.1 8 +/- 0.14 for the Eu III lambda 6666.347 line. This value is obtained with out taking into account a possible hyperfine-splitting which is unknown for this Eu III line. We also provide astrophysical gf-values for Eu III lambd a lambda 7221.838, 7225.151, and 8079.071.