Predissociation of H3 near its ionization threshold induced by very weak electric fields

We report the discovery of predissociation channels in H3 at energies within a few meV of the lowest ionization threshold. The predissociation affects selected p- and d-Rydberg states with high principal quantum numbers. For the d states, the predissociation process is induced by very weak electric fields, of order less than 1 V/cm. The predissociations are due to interaction with vibrationally excited states of low principal quantum number that exhibit significant coupling to the repulsive ground-state surface of H3, 2p2E'. We discuss the possible significance of these predissociation channels for decay paths in dissociative recombination of H3+ with low-energy electrons