Dissociation dynamics of C3O2 excited at 157.6 nm

C. E.M. Strauss*, S. H. Kable, G. K. Chawla, P. L. Houston, I. R. Burak

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The dissociation of carbon suboxide by single photon absorption at 157.6 nm has been studied under the collisionless environment of a molecular beam. The primary products are 2CO + C [3P(97%) or 1D(3%)]. The spin-orbit levels of the 3P carbon are statistically distributed. The CO rotational populations in the first four vibrational levels are found to be well described by Boltzmann distributions with temperatures 3430, 4120, 4670, and 2340 K for ν = 0,1,2,3, respectively. A second low temperature component in the ν = 0 rotational distribution is attributed to CO produced in coincidence with C(1D). Significant population is found in the first four vibrational levels with less than 3% estimated in the higher levels; a vibrational temperature of 3700 K fits the distribution. Analysis of the Doppler profiles of the CO and carbon suggest that the dissociation is stepwise; the first dissociation appears to be described by an anisotropy parameter near β = 2, while the second appears to be isotropic. The mean CO fragment speeds were nearly constant for all rotational levels, though slightly faster for ν = 1 than ν = 0. From the translational energetics of the CO at least a small amount of stable C2O is inferred to exist. The overall energetics place the stable C2O quantum yield under 2% assuming that excited C2O is not radiatively stabilized. We were unable to detect C2O directly in any electronic state. The dissociation of C 3O2 into C(3P) + 2CO appears to be best described as a stepwise reaction that produces a nearly statistical partitioning into all fragment degrees of freedom. The best agreement is obtained for an intermediate C2O electronic state in the vicinity of the b̃ state (e.g., b̃, ã or Ã)2; a ground state C 2O intermediate is unlikely. The singlet to triplet crossing most likely occurs in the C2O system on a time scale longer than a rotation (a few picoseconds).

Original languageEnglish
Pages (from-to)1837-1849
Number of pages13
JournalThe Journal of Chemical Physics
Issue number3
StatePublished - 1991


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