NEAR-THRESHOLD CONTINUUM STRUCTURE AND THE DISSOCIATION-ENERGIES OF H-2, HD, AND D(2)

Using laser double-resonance spectroscopy, we have studied the second dissociation limit of all three stable isotopic variants of molecular hydrogen. Just above threshold, the vibrational continuum exhibits con siderable fine-grained structure, differing greatly between isotopes b ecause of varying nonadiabatic couplings between the B, B', and C stat es. Significantly improved values of the dissociation energies are obt ained from the continuum onsets. We also report preliminary investigat ions of atomic 2S:2P branching ratios very near threshold.