Measuring electron affinities with the photodetachment microscope

Photodetachment microscopy, which was originally proposed as a new method for direct measurements of ionization or detachment energies, has been applied for a determination of the electron affinity of oxygen. The electron affinities of [Formula Presented] and [Formula Presented] could be measured separately from a natural sample. The experimental values (obtained as wave numbers, to be multiplied by [Formula Presented] to give energy units) are 11 784.682 (20) and 11 784.612 (29) [Formula Presented], respectively. The measured [Formula Presented] fine structure of [Formula Presented] is 177.085 (27) [Formula Presented]. The observed discrepancy of the electron affinity of oxygen with the value admitted so far, 11 784.648(6) [Formula Presented], is yet unexplained.