HYPERFINE-STRUCTURE AND ISOTOPE SHIFT IN TL-II WITH ASTROPHYSICAL APPLICATIONS

Fourier transform (FT) spectra of Tl II with resolved hyperfine struct ure (hfs) have been analyzed in the region 1790-3400 Angstrom. Measure d isotope shifts (IS) for two transitions, including the S-1-P-3 inter combination line to the ground state at 1908.6 Angstrom are reported. Accurate Ritz wavelengths for isotope and hyperfine components of the S-1-P-1 resonance line at 1321.6 Angstrom are given. The accuracy is b etter than 0.3 m Angstrom for measured wavelengths and better than 0.4 m Angstrom for the Ritz wavelengths. Theoretical multi-configuration Dirac-Fock (MCDF) calculations, including core polarization, show that the LS-allowed 1321.6 Angstrom transition is a factor of 30 stronger than the intercombination line at 1908.6 Angstrom. The application of the new Tl II data to astrophysical spectra obtained with the Hubble S pace Telescope is discussed.