Observation of Direct Dissociative Ionization in Molecular Hydrogen

Direct dissociative ionization is the simplest three-body breakup process in H₂. We describe the experimental verification of direct dissociative ionization to the repulsive A²Σ_u⁺ state by resolving the kinetic energy and angular distributions of the formed protons. A (2+1) resonant enhanced multiphoton ionization process via the isotropic E,F¹Σ_g⁺(v = 6,J = 0) level is employed. The structure in the kinetic energy spectrum is well described by a projection of the vibrational wave function of the E,F¹Σ_g⁺(v = 6,J = 0) state onto the repulsive ionic state. The electronic character of the ionization continuum is revealed by the proton angular distribution.