Vibrational transitions above-threshold dissociation

Figure 1. Morse potential V(q), vibrational levels Ev, and wave functions < (q) for the model OH (adapted from Ref. 14). The arrows indicate various selective vibrational transitions as well as above-threshold dissociations (ATDs) induced by IR femtosecond/picosecond laser pulses, as discussed in Sections III.A-III.D see Figs. 3-5. Horizontal bars on the arrows mark multiple photon energies ha of the laser pulses cf. Table 1. The resulting ATD spectrum is illustrated by the insert above threshold.

The rigorous calculation of the absorption spectrum now proceeds in exactly the same way as outlined in Section 3.1.2 [see Equation (3.14)] with the exception that the transition dipole function is replaced by the dipole function [i.e., the diagonal element of the dipole matrix defined in Equation (2.35)] because the absorption takes place in the same electronic state. Below the first threshold, the spectrum is discrete because both vibrational states are true bound states. Above the n = 0 threshold, however, the system becomes open and can dissociate yielding Ar and H2(n = 0). The spectrum is consequently a continuous spectrum with sharp resonances near the quasi-bound states temporarily trapped by the... 

In summary, the present study has shown that the measured thresholds for dissociation of NO and 02" correspond quite closely to known adiabatic dissociation energies of these ions if the initial internal energy state of the reacting ion is taken into account. The energy required for these dissociations can be derived both from the kinetic energy and from internal excitation of the ionic reactant. These processes can therefore be interpreted as involving adiabatic transitions to the vibrational continuum above the dissociation limit of the ground states or excited states of the... 

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