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 ν 1 symmetric stretching mode, belonging to the a 1g representation, while the second one, which appears shifted by 440 cm −1 from the first, is caused by a simultaneous excitation of the ν 1 and ν 4 (t 1u) modes. The results are consistent with an O h symmetry of the SF 6 - anion.