Spectroscopy of molecular ions: Laser induced predissociation of O 2 +

The technique of laser induced predissociation and laser induced fluorescence is applied to study spectra of gas-phase molecular ions. The main feature of the experiment is a beam of mass selected molecular ions illuminated by a pulsed dye laser. Over an extended range of excitation energies spectroscopic information can be obtained about positive and negative ions including transient species. As a first result we present predissociation spectra of O ₂ ⁺ ,b ⁴ bE _g ^? ?a ⁴ π _u Δv=3 andgDv=2 which can well be simulated by calculated spectra assuming a rotational ion temperature of 300δK.