The complete state-resolved differential cross section sigma(v',j',theta;E-c), investigated in a crossed-beam scattering study, is presented for the title reaction at six initial collision energies (E-c) which are below or near the barrier energy. At low energies, all reactive flux is gated through a trapped resonance state via a tunneling process. Hence, it serves as a benchmark system for better understanding the reactive resonance phenomenon. In addition to highlighting various resonance fingerprints of experimental observable, the concept of resonant tunneling reaction mechanism is elucidated. Particular emphasis is placed on its distinction from the more conventional transition-state reaction mechanism.