Photoelectron spectroscopy of nickel group dimers: Ni−2, Pd−2, and Pt−2

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Abstract
Negative ion photoelectron spectra of Ni−2, Pd−2, and Pt−2 are presented for electron binding energies up to 3.35 eV at an instrumental resolution of 8–10 meV. The metal cluster anions are prepared in a flowing afterglow ion source. Each dimer exhibits multiple low‐lying electronic states and a vibrationally resolved ground state transition. Franck–Condon analyses yield the anion and neutral vibrational frequencies and the bond length changes between anion and neutral. The electron affinities are determined to be EA(Ni2)=0.926±0.010 eV, EA(Pd2)=1.685±0.008 eV, and EA(Pt2)=1.898±0.008 eV. The electronic configurations of the ground states are tentatively assigned. Comparison of the nickel group dimers to the coinage metal dimers sheds light on the d orbital contribution to the metal bonding in the nickel group dimers.