The resulting photoelectrons are projected onto a 2D detector comprising two chevron-stacked microchannel plates coupled to a phosphor screen, which is photographed by a CCD camera after each laser shot. Each image is analyzed for individual electron events for which the centroids are calculated and binned into a 1024 × 1024 grid. The three-dimensional electron velocity distribution is reconstructed from the accumulated images using an inverse-Abel method. The radial position of features in the reconstructed image is related to electron kinetic energy (eKE) by acquiring VMI images for detachment from atomic F¯ at several photon energies. The VMI spectrometer has an approximately constant resolving power, ΔeKE/eKE, 32 yielding the highest eKE resolution for slow photoelectrons. As such, a SEVI spectrum is acquired by first taking an overview spectrum at a sufficiently high photon energy to access all (or most) of the photodetachment transitions before tuning the detachment laser to energies slightly above features of interest. This procedure results in the collection of high-resolution spectra over narrow energy windows that are then concatenated and scaled to match intensities in the overview spectrum, which is less sensitive to variation of the photodetachment cross section with photon energy. Spectra are plotted as a function of electron binding energy (eBE), given by eBE = hv -eKE.