REMPI detection of singlet oxygen 1O2 arising from UV-photodissociation of van der Waals complex isoprene-oxygen C5H8-O2

Highlights: • Photodissociation of van der Waals complex isoprene-oxygen C₅H₈-O_2. • One-laser two-color REMPI of oxygen in excited singlet and ground triplet states. • Velocity map imaging of oxygen in excited singlet and ground triplet states. The one-laser two-color resonance enhanced multiphoton ionization REMPI [(1 + 1′) + 1] and velocity map imaging have been applied to investigate formation of molecular oxygen in excited singlet O₂($a^1{\Delta }_g$) and ground O₂($X^3{\Sigma }_g^{-}$) states in the photodissociation of van der Waals complex isoprene-oxygen C₅H₈-O₂. These molecules were found to appear in the different rotational states with translational energy varied from a value as low as ∼1 meV to a distribution with temperature of about 940 K. The observed traces of electron recoil in the images of photoions reveal participation of several ionization pathways of the resonantly excited intermediate states of O₂.