The line absorption technique was applied to the kinetic study of the two metastable atomic nitrogen states N (22D) and N (22P) in a flowing afterglow system. The optical absorptions of the NI 1493-Å (2p32D−3s2P) and 1743-Å (2p32D−3s2P) transitions were used for the quantitative measurement of N (22D) and N (22P) concentrations. Deactivation of N (2D) and N (2P) by the Pyrex tube wall was found to be very efficient, i.e., occurs at nearly every collision. The second-order rate constants at 300°K for the removal of N (2D) by O2, N2O, CO2, NO, N2, Ar, and He were found to be (6±2)×10−12, (3.5±1.2)×10−12, (5±2)×10−13, (7±2.5)×10−11, (1.6±0.7)×10−14, (1±0.6)×10−16, and ≤ 1.6×10−16 cm3 sec−1, respectively. It was established that the process for the first three reactant gases results in chemical reaction rather than physical quenching.

The rate constants for the reactions of OH with CℓO, Cℓ2, and Cℓ2O at 298K have been determined in a discharge flow system using resonance fluorescence detection. The results are (9.1 ± 1.3) × 10−12, (5.5 ± 0.3) × 10−14, and (6.5 ± 0.5) × 10−12 (all in units of cm³ sec−1), respectively. In the reaction of OH and CℓO the reaction product HO2 has been detected indirectly, and a lower limit of 65% has been established for the OH + CℓO → HO2 + Cℓ channel.

Gas-phase reactions of 0(1D) with CH* and with C2He were studied by the photolyses of N2O-CH4 and N2O-C2H6 mixtures using 1849-Á light. Pressure effects and radical scavenging techniques were used to identify the sources of the products. At low pressures, where stabilization of excited alcohol intermediates did not occur, the main path of the Oí1!)) + CH4 reaction was to form CH3 + OH radicals, which ultimately produce C2H6. Molecular elimination giving H2 + CH2O occurred to the extent of 9%, which is the same as when the reaction takes place in liquid Ar at 87°K. The main path of the Oí1D) 4-C2H6 reaction was to form C2H5 + OH and CH3 + CH2OH radicals, which ultimately produce n-C4Hio, CsHs, and ChHe as principal products. The total reaction does not proceed via ROH* intermediates. The OH radicals are produced both by fission of such intermediates and by direct abstraction of H atoms, in agreement with the results of Cvetanovic and coworkers. Comparison with previous results in liquid argon indicates that the condensed medium suppresses the abstraction reaction in favor of the insertion reaction. The molecular process giving CH2O + H2 also does not involve the CH3OH* intermediate, asshown by the fact that this path contributes equally both in the gas and liquid phases. (1) This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS 7-100, sponsored by the National Aeronautics and Space Administration. (2) (a) M.

The rate constant and temperature dependence of the Cl + CH4 reaction have been investigated by the techniques of competitive chlorination of CH4/C2H6 mixtures and by discharge-flow/mass spectroscopy. The objectives were to determine an accurate value for the rate constant for use in stratospheric modeling, and to clarify discrepancies in results previously obtained by different techniques. The results deduced from the competitive chlorination study are in good agreement with the absolute values measured by the mass spectrometric method, and at temperatures above 300 K are in good agreement with measurements by other techniques based on resonance fluorescence detection of atomic chlorine. However, in the 220-300 K region, the competitive experiments indicate lower rate constants than those obtained by resonance fluorescence methods, and do not reproduce the curved Arrhenius plots seen in some of those studies.

The absorption cross sections of hydrogen peroxide vapor in the wavelength range from 195 to 350 nm were determined at 296 K. The absorption cross sections of neutral aqueous solutions of hydrogen peroxide were also measured in the same wavelength range. The results are compared with those of other workers, and calculated photodissociation coefficients of atmospheric hydrogen peroxide are presented.