Abstract
SEVERAL plausible parent molecules may be proposed for cometary species such as H, OH, C2, CN and so on, but no parent molecule has been shown to produce C3 by primary photodissociation without the intervention of secondary collisions. Swings1 has considered the possibility that the parent molecule is diacetylene (H—C≡C—C≡C—H), and Callomon and Ramsay2 have observed C3 in absorption in the flash photolysis of diacetylene diluted with a high pressure of He. They suggest that the primary process may be C4H2 + hν→C3H + CH followed either by decomposition of C3H to C3 + H or by reaction of C3H with CH to form C3 + CH2. The first alternative does produce C3 without secondary collisions, but it could not be responsible for the observations in the flash photolysis experiments in a quartz vessel because the overall process C4H2→C3 + H + CH is not energetically possible above approximately 1057 Å (ref. 3). An additional complication is that product analysis from the continuous photolysis of diacetylene has led to the suggestion4 of primary processes such as C4H2 + hν→C2H2 + C2 and C4H2 + hν→2 C2H, although C2 was not seen in absorption in the flash photolysis experiments in isothermal conditions2.
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References
Swings, P., Quart. J. Roy. Astron. Soc., 6, 28 (1965).
Callomon, J. H., and Ramsay, D. A., Canad. J. Phys., 35, 129 (1957).
Cowperthwaite, M., and Bauer, S. H., J. Chem. Phys., 36, 1743 (1962).
Pontrelli, G. J., J. Chem. Phys., 43, 2571 (1965).
Gausset, L., Herzberg, G., Lagerquist, A., and Rosen, B., Astrophys. J., 142, 45 (1965).
McNesby, J. R., Actions Chimiques et Biologiques de Radiations, 9, 39 (1966).
Payne, W. A., and Stief, L. J., J. Chem. Phys. (in the press).
Stief, L. J., De Carlo, V. J., and Payne, W. A., J. Chem. Phys., 54, 1913 (1971).
Snyder, L. E., and Buhl, D., Bulletin AAS, 3, 388 (1971).
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STIEF, L. Origin of C3 in Comets. Nature 237, 29 (1972). https://doi.org/10.1038/237029a0
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DOI: https://doi.org/10.1038/237029a0
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