were made in the latter analysis to eliminate the difficulties arising from the variation of K with T and T. was not replaced by T, under the radical. The application of this method of analysis to TJ data taken at high filament temperatures is discussed elsewhere. 9 APPLICATION TO POLYATOMIC GASESThe discussion above has been directed entirely to the AC of monatomic gases. Any attempt to extend THE JOURNAL OF CHEMICAL PHYSICS the above argument to gases of more complex molecules seems bound to result in difficulties, since a different T i , a, b', and b should be assumed for each rotation and mode of vibration.For nonlinear molecules with equivalent identical nuclei an important pathway leading to equilibration of nuclear spin statistics isomers is provided by wavefunction mixing induced by the spin-rotation interaction and in some cases the spin-spin interaction. For CH. this mixing is very large and provides for very rapid equilibration of the three spin statistics isomers. For asymmetric rotor molecules such as H20 and CH20 the rapidity of the equilibration is sensitive to the exact rotational energy level pattern. The spin-rotation mixing may be very important if there is an accidental near degeneracy of the right sort. Then most of the isomerization "funnels" through the near-degenerate levels.

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Polanyi 1 clearly predicted the possibility of stimulated emission from HC1 due to selective vibrational excitation in the chemical reaction H + Cl 2 -HClt + CI. We have recorded such emission and laser oscillation in a few P-branch transitions of HC1 formed in reactions initiated by flash photodissociation of chlorine in a Cl 2 -H 2 mixture. We believe this is the first operating laser based upon excitation by a chemical reaction. Vibrational-rotational laser transitions have been observed earlier by Patel, Faust, and McFarlane 2 but by other means of excitation: C0 2 2 and CO 3 in electric discharges, andC0 2 4 and N z O 5 through transfer of vibrational energy from N 2 t.Emission was studied either from a Ramantype multiple-reflection cell 8 containing a flash photolysis tube, or from a 60-em, 14-mm i.d. quartz laser tube fitted with normally polished sodium chloride discs affixed at the Brewster angle. A third disc, tilted at a 10° angle, deflected 8.2% of the light out of the confocal cavity formed by two gold-surfaced mirrors (radius, 1 m) placed 86.5 cm apart. The emission from the multiple-reflection cell was studied with the rapid-scan spectrometer, sometimes 10 20 30 TIME (>iSEC)FIG.

Ihfrared kinetic spectroscopy using excimer laser flash photolysis and color center laser probing has been used to study the NH, + NO reaction. The amidogen radical, NH2, was produced by ArF photolysis of NH3. Infrared absorptions of OH and H 2 0 were measured to determine the absolute contributions of the OH and HzO product channels. It was found that the OH channel accounts for 13 * 2% of the reaction. Using two different pairs of NH, and H 2 0 lines, we measured values of 0.85 * 0.09 and 0.66 h 0.03 for the ratio of H 2 0 formed to NH3 photolyzed. All of the H 2 0 signals exhibit a pronounced induction period suggesting that H 2 0 is produced in very high vibrational states. The time evolution of low-lying vibrationally excited and ground vibrational state H 2 0 lines is adequately simulated by a model in which a stepwise sequential loss of vibrational energy occurs with quenching cross sections for each step proportional to excess energy.

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