Dissociation dynamics of quasibound levels in the g 3 Σg state of H2: Characterization of the continuum

Decay pathways and photofragment anisotropy parameters have been determined for a series of rovibrational levels of the g³Σ⁺_g state in molecular hydrogen using fast-beam photofragment spectroscopy. The g ³Σ⁺_g(v=4) levels are found to be weakly predissociated by homogeneous interaction with the lower lying n=2 a 3Σ⁺_g state and by rotational coupling with the i ³ π_g state. The observed photofragment anisotropy reveals fine and hyperfine structure depolarization. The decay of g ³Σ⁺ _g (v=5) levels is dominated by barrier tunneling. The anisotropy parameters identify the symmetry of the continuum to be of mixed Σ _g and π_g character, which implies that hydrogen molecules can tunnel through two different barriers. The determination of the kinetic energy and the anisotropy parameter of the photofragments have resulted in a number of spectral reassignments.