Time-of-flight study ofH(2S)andD(2S)produced by electron impact onH2,D2, and HD: Evidence for predissociation

Time-of-flight spectra of $\mathrm{H}\mathrm{}\left(2S\right)\mathrm{}$ and $\mathrm{D}\mathrm{}\left(2S\right)\mathrm{}$ fragments from electron-bombardment-dissociated ${\mathrm{H}}_2$, ${\mathrm{D}}_2$, and HD have been observed. Structure in the kinetic-energy distributions below 1.3 eV is interpreted as arising from predissociation of bound vibrational levels. For ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ the primary predissociation process appears to be predissociation of the D state via the $B^{\prime }$ state. Predissociation structure for HD, although more prominent than for ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$, is not as easily interpreted. Evidence for the direct dissociation of the $B^{\prime }$ state has also been obtained and the relative probabilities of direct dissociation and predissociation have been estimated.