High-pressure range of the addition of HO to HO .3. Saturated laser-induced fluorescence measurements between 200 and 700 K

The addition of HO to HO was studied by saturated laser induced fluorescence at temperatures between 200 and 700 K and at pressures of the bath gas helium up to 100 bar. In combination with earlier measurements at 298 K, a set of falloff curves is constructed for the given temperature range. The limiting high-pressure rate constant for the reaction HO+HO(+He)-->H2O2(+He) follows as k(l,infinity)=(2.6+/-0.8)X10(-11) (T/300 K)(0+/-0.5) cm(3) molecule(-1) s(-1), practically independent of the temperature between 200 and 400 K. At higher temperatures, k(l,infinity) decreases. These results serve as a reference for statistical adiabatic channel model calculations of the recombination rate. (C) 1996 American Institute of Physics.