Figure 5.

The fraction (%) change of transient C₂F₄I radicals (diamond), final product C₂F₄ (closed circle), and parent C₂F₄I₂ (open square), as a function of delay time. The error bars are one standard deviation. The solid curves are from the solution of the kinetic model, Eq. 3, with τ₂ = 17 ± 2 ps for C₂F₄ data. For the decay of C₂F₄I, τ₂ was found to be 18 ps, but the error bars are somewhat bigger. In the fitting, the first C—I bond breakage was taken as a step function, since it occurs in ≈200 fs; convolution with our time resolution was included (see text). The inset shows the clocking (zero-of-time) with better than 2 ps accuracy. Note that the fraction of reacted parent molecule detected at the time zero is half of the final fraction, and this is entirely consistent with the fact that the first bond breakage is much shorter than 10 ps. This observation also confirms the accurate clocking (2 ps) of time zero in these experiments, as shown in the inset.