Unpacked cell, reaction

Also supporting wall reactions is the experiments in excess He. He, an inert gas, reduces the rate coefficient which indicates that either the chain termination steps require a chaperone gas or that initiation is a diflFusion-controUed wall reaction. Since the He eflFect is much more pronounced in the unpacked cell, the latter of the two possibilities is supported. 

When NH3 is added to O3 in the reaction vessel, the O3 is consumed, and a white solid aerosol is produced which settles on the cell walls. The O3 consumption is monitored by its intense absorption at 2537 A. For a freshly cleaned cell some decay of the O3 occurs even in the absence of NH3. However the reaction with NH3 is much more rapid but is not reproducible. As the solid deposit accumulates from several runs, the background reaction becomes negligible, and the reaction with NH3 becomes slower and reproducible. All reported results here are for the cell (packed and unpacked) conditioned this way. 

Figure 3. Plot of the change in optical density at 3000-4200A (mainly 3660A) vs. reaction time for several runs in the unpacked and packed reaction cell. At these wavelengths the reactants do not give measurable absorption. The change in optical density is caused by aerosol formation.

Figure 6. Plot of the square of the ratio of the rate constant in the absence of He, to that in the presence of He, k, vs. the He pressure in the unpacked and packed reaction cell (the values for ko were taken from Figure 5 at the values of [Og lo/lNHs ] corresponding to each k)...

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