Hyperfine structure and isotope shift in Tl II with astrophysical applications

Abstract

Fourier transform (FT) spectra of Tl II with resolved hyperfine structure (hfs) have been analyzed in the region 1790-3400 Angstrom. Measured isotope shifts (IS) for two transitions, including the S-1-P-3 intercombination 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 better 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 Space Telescope is discussed