Adiabatic and nonadiabatic decay

While all examples discussed in the foregoing sections belong to the category of direct photodissociation we consider in this section three cases of indirect bond fission and the subsequent vibrational state distributions. We will focus our attention on the question, how do the final distributions reflect the fragmentation mechanism  

As estimated from the widths of the partial absorption cross sections, the lifetime varies from 15 fe to 70 fs which corresponds, on the average, to merely one to four vibrational periods of NO within the T complex. The photodissociation of ClNO(Ti) is thus a hybrid of direct and indirect dissociation. 

Dixon and Rieley (1989) measured a ratio of a(n = 1) a(n = 2) a n = 3) of 2 1 0.01 for excitation in the n = 2 band. The calculated ratio shows the same overall trend, i.e., a decrease with n but without the result for n = 0, which experimentally could not be determined for technical reasons, the comparison between theory and experiment remains incomplete. 

In this chapter we discuss only the scalar aspect of rotational excitation, i.e., the forces which promote rotational excitation and how they show up in the final state distributions. The simple model of a triatomic molecule with total angular momentum J = 0, outlined in Section 3.2, is adequate for this purpose without concealing the main dynamical effects with too many indices and angular momentum coupling elements. The vector properties and some more involved topics will be discussed in Chapter 11. 

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