Photodissociation dissociation

In an FT-ICR instrument, fragmentation may be achieved by colliding ions with neutrals (CID) but various other strategies are available, such as collision with surfaces (surface-induced dissociation) or bombardment with ultraviolet or infrared radiation from a laser (ultraviolet photodissociation and multiphoton infrared photodissociation). Dissociation may also be achieved by the absorption of black-body radiation produced by a heated vacuum chamber walls (blackbody infrared dissociation). An advantage of these radiation-induced fragmentation methods is that gas pulses are no longer required. Sustained off-resonance irradiation is the preferred, radiation-based method for FT-ICR MS because it is the simplest to implement and tune. Very low energy and multiple excitation collisional activation techniques are also available. 

Lin C Y and Dunbar R C 1994 Time-resolved photodissociation rates and kinetic modeling for unimolecular dissociations of iodotoluene ions J. Rhys. Chem. 98 1369-75... 

Figure 3, Wavepacket dynamics of the photodissociation of NOCl, shown as snapshots of the density (wavepacket amplitude squared) at various times, The coordinates, in au, are described in Figure b, and the wavepacket is initially the ground-state vibronic wave function vertically excited onto the 5i state. Increasing corresponds to chlorine dissociation. The density has been integrated over the angular coordinate. The 5i PES is ploted for the geometry, 9 = 127, the ground-state equilibrium value,...

Irradiation of the molecular radical anion of DESO, which has a yellow color, with light of X = 350-400 nm partially restores the red color and the ESR spectrum of the radical-anion pair. Similarly to the case of DMSO-d6 a comparison of the energetics of the photodissociation of the radical anion and dissociative capture of an electron by a DESO molecule permits an estimation of the energy of the hot electrons which form the radical-anion pair of DESO. This energy is equal to 2eV, similarly to DMSO-d6. The spin density on the ethyl radical in the radical-anion pair of DESO can be estimated from the decrease in hfs in comparison with the free radical to be 0.81, smaller than DMSO-d6. 

The problem of controlling the outcome of photodissociation processes has been considered by many authors [63, 79-87]. The basic theory is derived in detail in Appendix B. Our set objective in this application is to maximize the flux of dissociation products in a chosen exit channel or final quantum state. The theory differs from that set out in Appendix A in that the final state is a continuum or dissociative state and that there is a continuous range of possible energies (i.e., quantum states) available to the system. The equations derived for this case are... 

This chapter has provided a brief overview of the application of optimal control theory to the control of molecular processes. It has addressed only the theoretical aspects and approaches to the topic and has not covered the many successful experimental applications [33, 37, 164-183], arising especially from the closed-loop approach of Rabitz [32]. The basic formulae have been presented and carefully derived in Section II and Appendix A, respectively. The theory required for application to photodissociation and unimolecular dissociation processes is also discussed in Section II, while the new equations needed in this connection are derived in Appendix B. An exciting related area of coherent control which has not been treated in this review is that of the control of bimolecular chemical reactions, in which both initial and final states are continuum scattering states [7, 14, 27-29, 184-188]. 

Resonance Enhanced Photodissociation FeO States Below the Dissociation Limit... 

Unfortunately, predissociation of the excited-state limits the resolution of our photodissociation spectrum of FeO. One way to overcome this limitation is by resonance enhanced photodissociation. Molecules are electronically excited to a state that lies below the dissociation limit, and photodissociate after absorption of a second photon. Brucat and co-workers have used this technique to obtain a rotationally resolved spectrum of CoO from which they derived rotational... 

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