Infrared spectroscopy of mass-selected metal carbonyl cations

► Metal carbonyl cations are produced in a molecular beam by laser vaporization. ► Ions are mass-selected and studied with IR photodissociation spectroscopy. ► C-O stretching frequencies are measured for M(CO)n+ cations for n = 1-9. ► C-O frequencies for cations are compared to those for neutrals. ► Stable coordination numbers vary from two to eight for different metals.