Decomposition rates for H2, diluted in Ar, were studied behind incident shock waves over the temperature range 2900° to 4700°K. HCl and the infrared emission from this molecule were used in a manner to trace the course of decomposition of the H2. In terms of recombination rate constants, we found (cc, moles, sec units) k−3=1018T−1, k−4=2.5k−3, and k−5=20k−3, where the subscripts 3, 4, and 5 refer respectively to Ar, H2, and H as third bodies.

Shock-tube kinetic studies of SF6 dissociation in argon have been made in the temperature range of 1650°–2050°K at pressures from 0.13–30 atm. Rate constants for the initial fragmentation of SF6 have been determined and have been found to be explainable in terms of classical unimolecular reaction kinetics. The analysis of the data in terms of the RRK theory yielded S = 6, λD = 0.25, E0 = 75.92 kcal/mole, and A = 1012.95sec−1 as the best values of the unimolecular parameters. The data did not rule out values of 5 to 7 for S or a factor of 2 range in λD with corresponding variations of about 4 kcal/mole in E0 and a factor of 3 in A. E0 = 75.92 kcal/mole represents the strength of the first S–F bond. Both ir and uv techniques were used to obtain the data.

The dissociation of Cl2 in Cl2–Ar mixtures was measured in a shock tube over the temperature range 1700° to 2500°K. Direct absorption spectrophotometry was used to follow the course of the reaction. A rate constant given by k=8.90×1013 exp —48 300/RT cm3/mole-sec [or,alternatively,k=3.13×1012(57 080/RT)2.087exp−57 080/RT cm3/mole·sec]was found to fit the measured data over the entire temperature range with a most probably error of ±6%. The activation energy determined agreed exactly with that measured by Hiraoka and Hardwick although the over-all rate constants were a factor of 10 lower than those reported by these investigators. Recombination rate constants, calculated from the measured dissociation rate constants by use of the thermodynamic equilibrium constant, were found to be in good agreement with the theoretical predictions of Benson and Fueno.

No abstract

A detailed kinetic model of the HCl chemical laser produced by the flash photolytically initiated H,-Cl, explosion is described, and the results of computer calculations on such a system are discussed. I t is shown that currently accepted values of the various rate constants, supplemented in a few cases by reasonable estimates of previously unmeasured rate constants, are adequate to approximate the observed laser behavior of this system. I t is also shown that the chemistry of such a system is extremely complex, and exhibits a high degree of coupling between one reaction and another; therefore, great care is required to extract kinetic data from the optical behavior of such laser systems. I t is further argued that different hydrogen halide lasers may behave quite differently from each other, depending on the relative magnitudes of the various rate constants involved.