Electron-Impact Excitation of the λ 190.8 nm and λ 179.9 nm Intercombination Lines in the Tl + Ion.

The results of experimental and theoretical studies on electron-impact excitation of the 6 s 6 p   P 1 °   3 → 6 s 2   S 0   1 (λ190.8 nm) and 6 s 7 s   S 0   1 → 6 s 6 p   P 1 °   3 (λ179.9 nm) intercombination transitions in the single-charged thallium ion are presented. The crossed-beams technique was used in combination with a spectroscopic method in the experiment. A distinct structure revealed in the cross-sections of both lines results from electron decay of atomic autoionizing states and radiative transitions from upper ionic levels. The dominant mechanism of the structure formation was the Coster–Kronig process. Relativistic distorted wave calculations were performed to obtain emission cross-sections for the above transitions. The absolute values of the cross-sections were found to be (0.25 ± 0.08) × 10⁻¹⁶ cm² (λ190.8 nm) and (0.10 ± 0.04) × 10⁻¹⁶ cm² (λ179.9 nm) at the electron energy of 100 eV. [ABSTRACT FROM AUTHOR]