Observation of Transition-State Vibrational Thresholds in the Rate of Dissociation of Ketene

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Science  12 Jun 1992:
Vol. 256, Issue 5063, pp. 1541-1544
DOI: 10.1126/science.256.5063.1541


Rate constants for the dissociation of highly vibrationally excited ketene (CH2CO) have been measured at the threshold for the production of CH2(3B1) and CO(1Σ+). The rate constant increases in a stepwise manner with increasing energy, consistent with the long-standing premise that the rate of a unimolecular reaction is controlled by flux through quantized transition-state thresholds. The data give the energies of the torsional and C-C-O bending vibrations of the transition state.