Dissociative decay ofn=3 levels inH2. II. Excited by laser from the metastable cΠu−3state ofH2

Fast-beam photofragment spectroscopy has been applied to study the photodissociation of metastable ${\mathrm{H}}_2$ molecules in the c ${}^3$ ${\Pi }_u^{\mathrm{-}}$ state, formed by charge exchange of ${\mathrm{H}}_2$ ${\mathrm{}}^{+}$ with Cs vapor. Transitions leading to radiatively dissociated or predissociated levels of the g, h, i, and j triplet gerade states of ${\mathrm{H}}_2$ are observed. The decay mechanisms, level positions, and, in the case of predissociations, the lifetimes are established for (ro-)vibrational levels (v≥4). The transitions to v≥5 levels of the j ${\mathrm{}}^3$ ${\Delta }_g$ state appear as asymmetric peaks with widths of around 50 ${\mathrm{cm}}^{\mathrm{-}1}$ (N=2). A calculation of the rotational coupling of the j state to the vibrational continuum of the i ${\mathrm{}}^3$ ${\Pi }_g$ state confirms this very rapid predissociation (τ≃${10}^{\mathrm{-}13}$ s). For v=4 of the j state, which couples to the continuum via the quasibound v=5 level of the i state, a relatively slow predissociation (τ≃${10}^{\mathrm{-}8}$ s) is observed.