Accurate nonadiabatic couplings for H3: Application to predissociation

Nonadiabatic coupling and vector correlation in dissociation of triatomic hydrogen

We determine experimentally the vector correlation among the three neutral ground state hydrogen atoms which appear in dissociation of neutral H3* molecules. The sum of the kinetic energies of the three H-atoms is fixed by selecting the energy of the H3* molecule by laser excitation in the range between 0.85 and 3.60 eV. The highly structured maps of correlation in the motion of the three atoms provide a direct view of the internal molecular couplings which initiate dissociation. We discuss this feature in a model calculation and in terms of a new quantum chemical calculations of the potential energy surfaces of H3*.

Maps of nonadiabatic coupling in triatomic hydrogen

We show in an experiment that dissociation of state-selected neutral H3* molecules into three ground-state hydrogen atoms reveals highly structured maps of correlation in the motion of the three atoms. These maps provide a direct view of the internal molecular couplings which initiate dissociation.

Channel mixing effects in the dissociative recombination of H+3 with slow electrons

We discuss the low-energy dissociative recombination of H+3, which strongly influences the abundance of this ion in diffuse interstellar molecular clouds. The kinetic couplings between the ionization continuum and the dissociative ground state of H3 have been used as input to a two-dimensional wave packet calculation of dissociation dynamics. The cross section obtained for direct dissociative recombination is much smaller than the latest experimental results. However, a multichannel quantum defect treatment shows that an indirect mechanism via bound Rydberg states of H3 prevails for this process.