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*.