Laser photoelectron spectrometry of Co− and Ni−

The photoelectron spectra of the negative ions Co− and Ni− have been obtained with a fixed frequency cw ArII laser (488 nm). The electron affinity of cobalt is found to be 0.662±0.010 eV, while that of nickel is 1.157±0.010 eV, in excellent agreement with a previously reported value E.A.(Ni) =1.15±0.15 eV determined by threshold photodetachment. Resolution of both negative ion and neutral fine structure intervals is obtained, and results in the determination of Co−: 3F4−3F3=910±50 cm−1, 3F3−3F2=650±50 cm−1 and Ni−: 2D5/2−2D3/2=1470±100 cm−1. The intensities of individual fine structure components are calculated from an angular momentum analysis of the photodetachment process and are compared with the experimental results. The fine structure intensities do not follow the (2J″+1) (2J′+1) statistical weighting of the negative ion (J″) and neutral (J′) spin–orbit states, but are much better represented by geometrical factors. The detachment of s electrons is preferred to the detachment of d electrons at 488 nm.