Measuring electron affinities with the photodetachment microscope

Photodetachment microscopy, which was originally proposed as a new method f or direct measurements of ionization or detachment energies, has been appli ed for a determination of the electron affinity of oxygen. The electron aff inities of O-16 and O-18 could be measured separately from a natural sample . The experimental values (obtained as wave numbers, to be multiplied by he to give energy units) an 11 784.682 (20) and 11 784.612 (29) cm(-1), respe ctively. The measured P-2(1/2)-P-2(3/2) fine structure of O-16- is 177.085 (27) cm(-1). The observed discrepancy of the electron affinity of oxygen wi th the value admitted so far, 11 784.648(6) cm(-1), is yet unexplained. [S1 050-2947(99)12305-9].