Nonadiabatic Feshbach

Nonadiabatic Feshbach calculations. Using the reaction-path Hamiltonian and invoking an adiabatic separation of the reaction coordinate from all other coordinates, resonance energies and adiabatic partial widths are obtained by neglecting all off-diagonal terms of the Hamiltonian. The most important... 

Resonances of the type illustrated in Figure 12.2 are called Feshbach resonances (Child 1974 ch.4 Fano and Rao 1986 ch.8 see also Figure 12.5). The quasi-bound states trapped by the Vn(.R) potential can only decay via coupling to the lower vibrational state because asymptotically the n = 1 channel is closed and therefore cannot be populated. This is different from the dissociation of CH30N0(Si), for example, [see Figure 7.10(a)] where the resonances can either decay via tunneling or alternatively by nonadiabatic coupling to the lower states. 

For the H + H2 case, we can compare the partial width calculations to predictions made by Poliak (146) using an RPO analysis. His calculations indicated that the adiabatic partial width is "negligible" coispared to the nonadiabatic one. Actually though, the accurate quantal results show an adiabatic/nonadiabatic ratio of 0.4, and the SCSA/Feshbach ratio is 0.3. 

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