Collisions, energy exchange

CFIDF end group, no selective reaction would occur on time scales above 10 s. Figure B2.5.18. In contrast to IVR processes, which can be very fast, the miennolecular energy transfer processes, which may reduce intennolecular selectivity, are generally much slower, since they proceed via bimolecular energy exchange, which is limited by the collision frequency (see chapter A3.13). 

Figure 1.5. Femtosecond spectroscopy of bimolecular collisions. The cartoon shown in (a illustrates how pump and probe pulses initiate and monitor the progress of H + COj->[HO. .. CO]->OH + CO collisions. The huild-up of OH product is recorded via the intensity of fluorescence excited hy the prohe laser as a function of pump-prohe time delay, as presented in (h). Potential energy curves governing the collision between excited Na atoms and Hj are given in (c) these show how the Na + H collision can proceed along two possible exit channels, leading either to formation of NaH + H or to Na + H by collisional energy exchange.

If the electron excitation energy of the atom A exceeds the ionization energy of the atom B, then during the collision of A and B atoms the ionization of the atom B is possible as a result of energy exchange between the electrons... 

Role of Excited States in Ion-Neutral Collisions 2. Energy Exchange a. Electronic Excitation... 

The observed angular-dependent shifts at the various collision energies are well described by (11.77). From the observed shifts the physically interesting quantity s/b can be determined by (11.77), which indicates the average location in the quasimolecule where the electron is ejected. It is found that s/b is always close to unity, which means that the electron comes from the helium. This is very direct evidence of the exchange mechanism of Pgl [see equation (11.69)]. 

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