Photodissociation from superposition state

Control over the a, and production of the desired superposition states can be achieved by several routes. One nice way is to utilize the reactants from an earlier photodissociation step, altering the af by any of a number of coherent control scenarios [2] for this piereactive step. Consider then preparing n, 0) via a prereactive stage in which an adduct AB, made up of a structureless atom A and the molecular fragment B, is photodissociated. The AB is assumed to be initially in a pure state of energy Eg and the photodissociation is carried out with a coherent source. Under these circumstances photodissociation produces B in a linear combination of internal states. For... 

Figure 3.28 Percentage yield of the H + OD channel in the photodissociation of DOH(0,2,0+ 1,0,0) superposition state. The excitation pulse bandwidth is 50 cm"1 >.ll dissociation pulse bandwidth is 50 cm 1, and the enter frequency is 71,600 cm"1. Ordinal j the detuning of the excitation pulse cox from the energy center of the (0,2,0) and (I o,0> states. (Taken from Fig. 3, Ref. [99].)...

Figure 5.3 Contour plot of I yield [I /(I + I )] for two color photodissociation of a fi CH3I superposition state composed of bound states with vibrational and rotational qua numbers (v, J) — (0, 2) and (1,2) excited with frequencies a>1 = 41,579 cm-1 and 1 41,163 cm-1. Contours increase, in increments of 0.04 from the center well . (Taken Fig. 1, Ref [175].)...

We have elucidated the nature of pulsed-shaping control of photodissociation from the viewpoint of energy-resolved coherent control theory. Clearly, when excitation is from a superposition of states, as in the vast majority of control scenarios, the role of the pulse shaping is to enhance a different set of interfering pathways for each control objective. 

Easy availability of ultrafast high intensity lasers has fuelled the dream of their use as molecular scissors to cleave selected bonds (1-3). Theoretical approaches to laser assisted control of chemical reactions have kept pace and demonstrated remarkable success (4,5) with experimental results (6-9) buttressing the theoretical claims. The different tablished theoretical approaches to control have been reviewed recently (10). While the focus of these theoretical approaches has been on field design, the photodissociation yield has also been found to be extremely sensitive to the initial vibrational state from which photolysis is induced and results for (11), HI (12,13), HCl (14) and HOD (2,3,15,16) reveal a crucial role for the initial state of the system in product selectivity and enhancement. This critical dependence on initial vibrational state indicates that a suitably optimized linear superposition of the field free vibrational states may be another route to selective control of photodissociation. 

Figure 4 Contour plot of the yield of a quantum state of the products m me photodissociation of CH3 I from a linear superposition of lEj > and IE3 >, to yield I + a) v=3, or b) v=4. The labelling of the abscissa and ordinate is as i Fig. 3...

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