The dissociation dynamics of rotating acetyl radical at energies near the threshold (19-23 kcal/mol) has been investigated by classical dynamics. Under microcanonical initial conditions and with zero total angular momentum, the dissociation of CH_3CO is intrinsically RRKM. When the rotational degrees of freedom are taken into account the phase space becomes non=ergodic. At 23 kcal/mol and for 6.7 ps, which is the average lifetime at this energy, between 15% and 40% of K_a space is mixed, suggesting that rotation-vibration coupling is modest, in agreement with experimental findings. Finally, excitation of the torsional mode decreases the rate by a factor of two.
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