High precision measurement of the 32SH electron affinity by laser detachment microscopy

The photodetachment microscopy technique, which was previously used with the OH− molecular anion, is applied successfully to the SH− ion with a single-mode dye laser. The interferograms of two rotational thresholds corresponding to particular detachment transitions of the SH−(X1Σ+; v = 0) → SH(X2Π3/2, 1/2;v = 0) band have been recorded. With a double-pass scheme of the laser excitation on the ion beam, pairs of interference patterns are obtained, the 2D fitting of which provides us with a new recommendable value of the electron affinity of 32SH, eA = 18669.543(12) cm−1, i.e., 2.3147282(17) eV. The precision on the determination of eA has been increased by three orders of magnitude in comparison with the previous 1981 determination retained by the most recent review on molecular electron affinities.