Chemical kinetics of hydrogen halide lasers. 1. The H₂Cl₂ system

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.

Review of Rate Data for Reactions of Interest in HF and DF Lasers.

“…In a study, 4 7 of DF(v I -4) relaxation by D 2 , the rate coefficients were found to scale with v as V 0 .5 exp(-AE.,/RT), where AE,, is the energy mismatch of the exchange. *(The exothermic exchange in the reverse direction scales simply as v*) Using this analogy and the measured rate coefficient for exchange (13a), we obtain for exchange (15) the rate coefficients, k., No evidence of multiquantum proceses$ was found in the studies' 3 of UV(v -3,4) deactivation by HNV, D 2 , N2.…”

“…In our 1976 review we listed (Table 1) all the experimental data of which we were aware pertaining to the absolute measurement of k 3 ; relative measurements of k 3 were tabulated separately (Table 2), because at the time the absolute measurements were not of themselves sufficiently unambiguous to allow a precise determination of k 3 with great confidence.…”

“…Furthermore, there is a difference in the activation energies reported by the two groups of investigators, but this can be partly accounted for by the ezistence of curvature n the Arrhenius plot of log k 3 versus I/T and the fact that the two studies were conducted over different temperature ranges. These experiments were carried out In the same facillties as were used to measure k 3 ; however, in this case there is no discrepancy between the room-temperature results of the two studies.…”

Flame-Sheet Analysis of C. W. Diffusion-Type Chemical Lasers, I. Uncoupled Radiation

“…(4)(5)(6)(7)(8)(9) and by Eqs. (10)(11)(12)(13)(14)(15), respectively. In many cases of interest, the pumping reactions are diffusion-limited and occur in a thin zone, which can be approximated by a flame sheet.…”

“…premixed, obviating the need to consider diffusion and convection effects altogether. 13 ) So that the presence of a nonequilibrium population distribution can be explicitly handled, the gas is treated as a mixture of several components, in much the same way as is done in the case of reacting gases, except that here each longlived vibrational level of the lasing molecule is treated as a separate component of the gas. Chemical formation of the lasing molecule by laminar mixing and combustion of fuel and oxidizer is assumed to be diffusion-controlled, i.e., combustion occurs along a flame sheet.…”