A translational spectroscopy technique is used to obtain predissociation kinetic energy release spectra from the lowest bound states of H3, 2sthinsp;2Arsquo;1and 2pthinsp;2Alsquo;2. These H@B3states are formed in nearhyphen;resonant electron capture by 3 keV H+3in Cs vapor. Their ground rovibrational levels are energetically about 1 eV above the H+H+H dissociation limit, thus all levels can yield both H2+H and the threehyphen;body products. The spectra contain both threehyphen;body and twohyphen;body components and are deconvoluted to obtain the branching ratios. Data obtained from two different ion sources show that the threehyphen;body/twohyphen;body ratio increases with increased rovibrational energy in the Hast;3. The results are compared to recent theory and with previously reported ratios from dissociative recombination of H+3. The comparison suggests that the ratio increases monotonically with the total electronic and rovibrational energy in the H@B3. Dast;3predissocation has a similar behavior. The Hhyphen; and Dhyphen;atom spectra from the twohyphen;body decay of HD@B2show that the ejected H atom is strongly favored on a perhyphen;atom basis.
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