Prompt dissociation

Our determined anisotropy parameters for 226 nm photolysis agree favorably with the reported values of Syage, where a (3 value of 1.2 was measured for the fast 0(3P2) products. Syage observed a less anisotropic distribution for the slow 0(3P2) atoms, with a reported (3 value of 0.4. The f3 value of 1.2 for the high velocity component was rationalized by a prompt dissociation from the equilibrium ground state of ozone following an B I >2 <— X A i transition. 

The prompt dissociation of the fast H atom in the pathway, for which character change and collapse of the 3s Rydberg orbital on the ethyl radical to the Is orbital of the H product are required,121-123 could be assisted by the conical intersection. Also, relaxation and internal conversion from the 3s state to the ground state ethyl can be facilitated by this conical intersection, in addition to other possible vibronic couplings in the A symmetry.39... 

Figure 12, Schematic mechanism for impulsive reaction of thermal energy reaction of K with oriented CF3I. The electron is assumed to be transferred at large distance to the molecule irrespective of orientation. The molecular ion is formed in a repulsive state that promptly dissociates, ejecting the T ion in the direction of the molecular axis, and the K is dragged off by the departing T resulting in backward scattering for heads orientation and forward scattering for tails as observed.

Reactions with still a first long-range electron transfer, but in a situation where the molecular anion could promptly dissociate. The illustrative example will be the Ba O3 —> BaO + O2 reaction. 

At increasing O2 pressure, one observes a decrease in epoxide selectivity and a steady increase in reaction rate [24]. Both effects are coupled and related to the competitive O2 addition to the ROO -to-C=C adduct, as shown in Figure 1.7. Indeed, this leads to the formation of a new type of peroxyl radical that will ultimately yield a dialkyl peroxide that promptly dissociates to new radicals due to the very weak 0-0 bond (see Table 1.1). 

Not included in the analysis of Refs. 55, 62 or 66 is the possible effect of the change in J (or F) of the parent JKM> state upon photoexcitation however, under the assumption of prompt dissociation, the framework of the molecule cannot reorient appreciably in the few hundred femtoseconds before the excited state falls apart, so the experimental results should be compared to calculations without change in quantum numbers. 

Prompt dissociations occur on a timescale equal to or less than the desorption event. 

Ions produced with lifetimes longer than those of excited ions that decompose in the ion source (prior to about 10 s) are called metastable ions. The existence of metastable ions can be explained by different mechanisms depending on the size and property of the precursor ion. Normally, dissociation of an excited ion occurs during the first vibration (prompt dissociation), or predissociation that involves a transition from one potential energy hypersurface to another, which also occurs rapidly ... 

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