Analysis of the hyperfine and isotopic structure of Ga II in the optical spectrum of κ Cnc and HR 7775

Spectra of the HgMn stars κ Cnc and HR 7775 have been analyzed, under the assumption of local thermodynamic equilibrium (LTE), with respect to the abundance and isotopic mixture of gallium. The primary purpose of the investigation was to level the contradictory results obtained using spectral lines in different spectral regions (Smith 1996). The analysis has been performed by Ga ii lines in the optical region including hyperfine and isotopic components from new Fourier Transform Spectrometer measurements (Karlsson & Litzén 2000). Gallium has, for both stars, been determined to be overabun-dant by two orders of magnitude compared to the sun, using oscillator strengths derived by Ryabchikova & Smirnov (1994). The difference in abundance obtained using spectral lines in the UV and the visual spectral region is unexplainable by accounting for hyperfine and isotopic structure. Astrophysical log gf values have been determined for the Ga ii 5p − 5d transitions at 5360, 5363 and 5421Å.