Laser photoelectron spectrometry ofFe−: The electron affinity of iron and the "nonstatistical" fine-structure detachment intensities at 488 nm

With a fixed-frequency Arii laser (488 nm), the photoelectron spectrum of ${\mathrm{Fe}}^{-}$ has been obtained. The electron affinity of iron is 0.164 ± 0.035 eV. It has been found that the cross section for detachment of $s$ electrons is much larger than that for detachment of $d$ electrons at this wavelength. Also, the various fine-structure transitions do not occur in the ($2J^{\prime \prime }+1\mathrm{}$) ($2J^{\prime }+1\mathrm{}$) statistical weighting of the neutral ($J^{\prime }$) and ion ($J^{\prime \prime }$) spin-orbit states. An explanation for this result extends previous calculations, deriving explicit, usable expressions for fine-structure transition intensities, which are then found to agree with those observed experimentally.