Electron affinities of [Formula Presented] [Formula Presented] [Formula Presented] the fine structure of [Formula Presented] and the hyperfine structure of [Formula Presented]

Photodetachment microscopy has been used in a double-pass, field-collinear scheme in order to measure the electron affinity of atomic oxygen. As an illustration of the sensitivity of the method, electron images could be recorded even from the rarest [Formula Presented] ion. Analysis of photodetachment images recorded with this odd isotope, however, requires that one knows the unresolved hyperfine structures of the ground states of both the neutral atom [Formula Presented] and the negative ion. Calculation of the hyperfine structure of [Formula Presented] was achieved, which permitted to add the electron affinity of [Formula Presented] to the series of the measured electron affinities of oxygen isotopes. The anomalous isotope shift of these electron affinities is finally compared with ab initio calculations.