0 -+ HF + 2F (2). The asterisks indicate a vibrationally excited molecule. Rate coefficients derived for these reactions depend slightly on the computational model. For a model that is adiabatic and in which HF(O) is not absorbed on the wall, 6 X 10 4 < k [ < 2 X 10 5 and 5 X 10 6 < k, < 7 X 10 6 cm 3 /mol-s when all vibrationally excited molecules of HF and H, are included in HF* and H, *. For a model that includes flow of heat out of the reacting gas and also diffusion of HF(O) to the wall, the coefficients are 6X10 4 < k[ < lX10 5 and 2X10 6 < k, < 5X10 6 cm 3 /mol-s. The computations show that quenched reactions take place during the time of experimental manipulation, so that the stability of H,-F,-O, and H,-F,-O,-M mixtures can be due in large measure to the HF produced during mixing. Double explosions and oscillatory reactions can also occur.The data in Ref. 3 are sufficiently extensive and precise to warrant analysis using a chemical mechanism containing all the elementary reactions that occur and for which rate coefficients are known or can be estimated within bounds. Very recent work l3 -ao on the rates of vibrational relaxation of HF 13 -17 and Ha 18-ao allows us to use measured rate coefficients for these important reactions. Also, recent work a1 -a4 on the quenching reaction H+ Oa+ M-HOa+ M provides rate coefficients for a number of inert gases M.

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