Spectroscopy of the Ca+–acetylene π complex

Abstract

Ca + – C 2 H 2 is produced in a molecular beam and studied with mass-selected photodissociation spectroscopy. A spectrum with sharp vibrational and rotational structure is measured near the Ca+ (2P←2S) transition. Ca+–C2H2 has a π-complex structure with a Ca+–C2H2 bond distance of r0″=2.80±0.20 Å, a vibrational frequency (Ca+–C2H2 stretch) of ΔG1/2″=169 cm−1, and a dissociation energy of D0″=18.6±5.0 kcal/mol. This is the first spectroscopic determination of these properties for an isolated metal cation π complex.