Nonstatistical Unimolecular Decay of the Singly Fluorinated Criegee Intermediate syn-FCHOO.

is an order of magnitude slower than that predicted by statistical unimolecular reaction theory with quantum mechanical tunneling. The nonstatistical behavior originates from excitation of a CH stretch vibration that is orthogonal to the heavy atom motions along the reaction coordinate and slow intramolecular vibrational energy redistribution due to the sparse density of states.