The fine structure of S and S− measured with the photodetachment microscope

Abstract

Photodetachment microscopy of a beam of 32S− ions makes it possible to measure the detachment thresholds corresponding to different fine-structure levels of the negative ion S− and the neutral atom S. The electron affinity of sulfur, at 2.077 eV, is well suited for detachment by a tunable dye laser, which provides a third way of measuring neutral S fine structure, besides VUV spectroscopy of S I lines and direct fine-structure resonance spectroscopy. The fine-structure intervals are found to be 48 353.52(34) m−1 for the 2P1/2 − 2P3/2 energy difference in S−, and 39 605.87(32) m−1 for the 3P1 − 3P2 one in S (with expanded uncertainties), consistent with an independent measurement of the 3P0 − 3P1 interval. The new recommended electron affinity for isotope 32 of sulfur is 1675 297.60(42) m−1, or 2.077 104 18(71) eV.