  Chemical reactions in the quantum degenerate regime are described by mixing
of matterwave fields. Quantum coherence and bosonic enhancement are two unique
features of many-body reactions involving bosonic reactants and products. Such
collective reactions of chemicals, dubbed "super-chemistry", is an elusive goal
in quantum chemistry research. Here we report the observation of coherent and
collective reactive coupling between Bose condensed atoms and molecules near a
Feshbach resonance. Starting from an atomic condensate, the reaction begins
with a rapid formation of molecules, followed by oscillations of their
populations in the equilibration process. Faster oscillations are observed in
samples with higher densities, indicating bosonic enhancement. We present a
quantum field model which describes the dynamics well and identifies three-body
recombination as the dominant reaction process. Our findings exemplify the
highly sought-after quantum many-body chemistry and offer a new paradigm for
the control of quantum chemical reactions.
