Franck–Condon analysis of the electron photodetachment spectrum

The electron photodetachment spectrum of the SF 6 - anion is analyzed in terms of the Franck–Condon factors between the anion and the neutral species. It is shown that the most intense progression can be easily assigned to the excitation of the ν1 symmetric stretching mode, belonging to the a1g representation, while the second one, which appears shifted by 440 cm−1 from the first, is caused by a simultaneous excitation of the ν1 and ν4 (t1u) modes. The results are consistent with an Oh symmetry of the SF 6 - anion.