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PHYSICAL CHEMISTRY Registered in U.S. Patent Ofice @ Copyright, 1978, by the American Chemical Society
VOLUME 76, NUMBER 1 JANUARY 6,1972
Rate Constants for Quenching of N,(A3ZC,+) in Active Nitrogen
by J. A. Meyer, D. W. Setser, and W. G . Clark Chemistry Department, Kansas State University, Manhattan, Kansas 66608 (Receiued June 3, 1971) Publication costs assisted by the Petroleum Research Fund
Mercury 2537 emission was used to monitor the concentration of Nz(A38,+)in active nitrogen at room temperature. Analysis of the quenching of the mercury emission upon the addition of reagent gases permitted the measurement of rate constants for removal of N2(ASZ,+) by the reagent gas relative to the rate constant for removal by nitrogen atoms. Since the nitrogen atom removal rate constant previously has been measured, the method gives absolute values for the rate constants. Eleven gases were investigated, and the magnitude of the rate constants ranged from 1.4 x 1014 cmS mol-’ sec-l for NH3 to 31 kcal are not consistent with the excess energy associated with reaction 1 being statistically partitioned. Either a CHz('A1) in a higher vibrational state or the production of the electronically excited CHz('B1) would account for this discrepancy. Circunistantial evidence favors the latter, though any choice with the available data is speculative.
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Introduction Despite the simplicity of the molecule, the photolysis of propane has been demonstrated to give a com-
plex product mixture. Not only does one find products rationalized on the basis of elimination of free radicals and small molecules from propane, but also a number of products which would appear to arise from secondary decomposition of the fragments produced in the primary photochemical process.
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To trace successfully the course of events commencing with the absorption of a photon and terminating with a collection of thermalized products, it is necessary to have some knowledge of the nature of the excited state(s) involved in the process. Propane is known to have a strong absorption spectrum in the vacuum ultraviolet.' The order of magnitude of the (1) H. Okabe and D. A. Becker, J . Chem. Phys., 39, 2549 (1963).
The Journal of Physical Chemistry, Vol. 76, N o . 1, 1972
