Molecular Photodetachment Microscopy

The photodetachment microscopy technique, which was originally used with atomic negative ions, is now applied to a molecular anion. The interferograms of several rotational thresholds corresponding to transitions from [Formula presented] [Formula presented] [Formula presented] states to OH [Formula presented] [Formula presented] states have been recorded. No effect due to the [Formula presented] dipolar potential of the neutral molecule appears. Using a double-pass scheme of the laser on the negative ion beam, we measure the energy of the first few detachment thresholds with improved accuracy. The new recommended value of the electron affinity of [Formula presented] is [Formula presented], or 1.8276503(17) eV.