Internal vibrational energy redistribution

Depopulation of S]. It is now useful to define a number of transformation channels available to an "isolated" molecule on its SVL of the state. They are fluorescence emission (F) through Si - So radiative decay, Sj-/vvW Sq, internal conversion (IC), S -AVW intersystem crossing (ISC), isomerization or decomposition (D), and time evolution of the vibrational state (TEV or vibrational energy redistribution). All of these non-radiative processes can be collision-induced, and the efficiency of collision-induced relaxation can vary with the nature of the collision partner, pressure, and other experimental parameters. 

In this chapter we survey characteristic features of time-dependent quantum wave-packet dynamics on conically intersecting potential-energy (PE) surfaces. The focus will be on the fully microscopic description of nontrivial dynamical processes such as ultrafast internal conversion and photoisomerization, as well as vibrational energy redistribution and dephasing. The quantum dynamics calculations discussed in this chapter are... 

R. Naaman, D. M. Lubman, and R. N. Zare, Vibrational energy redistribution in glyoxal following internal conversion, J. 

Vibrational Predissociation, in this section we discuss the case of a transition from a predissociative state to the photofragment state that occurs on a single adiabatic pes. Such processes cannot occur for diatomic molecules, but they can be observed for polyatomic systems. The transition is caused by intramolecular energy transfer, that is, by internal redistribution of vibrational energy. 

Fig. 1.2. Schematic illustration of electronic (a) and vibrational (b) predissociation. In the first case, the molecule undergoes a radiationless transition (rt) from the binding to the repulsive state and subsequently decays. In the second case, the photon creates a quasi-bound state in the potential well which decays either by tunneling (tn) or by internal energy redistribution (IVR).

By inelastic resonances we mean resonances which decay via energy redistribution between the internal vibrational-rotational modes or a transition from a quasi-bound to a continuum state. Elastic resonances, on the other hand, decay via tunneling through a potential barrier without the necessity of internal transitions. 

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