Double-resonance study of predissociation of the j/sup 3/. delta. /sub g/ state of H/sub 2/

A photoionization-photodissociation double-resonance technique has been employed to excite transitions from selected rovibrational levels of the metastable c /sup 3/Pi/sub u//sup -/ state to the rapidly predissociated j /sup 3/..delta../sub g/ state of H/sub 2/. The photodissociation resonances arise from the configuration interaction between the j /sup 3/..delta../sub g/ and i /sup 3/Pi/sub g/ states, and exhibit the asymmetry of Fano-Beutler profiles. These resonances have widths that decrease with increasing v' from 29 to 10 cm/sup -1/; calculated predissociation widths show the same vibrational trend but are consistently 30% smaller. Results have been obtained for the rovibrational energy spacings of high-v levels within each state, and are in good agreement with theory. Photon energies for the c-to-j state transitions are slightly larger than those predicted theoretically.