Competition among autoionization, predissociation, and ion-pair formation in molecular hydrogen

摘要

We have investigated autoionization, predissociation, and ion-pair formation highly excited states of molecular hydrogen by using double-resonance excitation via the E,F (sup 1)(Sigma)(sub g)(sup +), v=6 level. The energetic threshold for ion-pair formation occurs just below the H(sub 2)(sup +) (times) (sup 2)(Sigma)(sub g)(sup +), v(sup +)=9 ionization threshold. The spectrum in this region was studied by using conventional and constant-ionic-state photoelectron spectroscopy, by monitoring the H(sup (minus)) production, and by detecting dissociation products by ionization with a third laser. The decay dynamics in this region are extremely rich, because the excited levels may decay by rotational and vibrational autoionization, by predissociation to neutral H + H* (n=2,3,4), by predissociation to the ion pair H(sup +) + H(sup (minus)), and by fluorescence. In addition, the dissociative potential curve of the 2p(sigma)(sub u)3s(sigma)(sub g) (sup 1)(Sigma)(sub u)(sup +) doubly excited electronic state crosses the H(sub 2)(sup +) (times) (sup 2)(Sigma)(sub g)(sup +) potential curve in the same energy ion, and the electronic autoionization of this state is found to significantly influence these decay processes.