Selective Photodynamic Control of Chemical Reactions: A Rayleigh-Ritz Variational Approach

Selective control of HOD photodissociation using CW lasers

“…[33][34][35] Furthermore, to exploit the dependence of photodissociation outcome on the initial vibrational state subjected to the photolysis pulse, we have been advocating the use of field optimized initial state (FOIST) scheme [36][37][38] which attempts to distribute the onus for selective control on both the field attributes and the molecular initial state subjected to the chosen photolysis pulse. The field attributes may be chosen for simplicity and chemical insight, and an optimal initial state is generated using FOIST.…”

“…The field attributes may be chosen for simplicity and chemical insight, and an optimal initial state is generated using FOIST. The FOIST scheme has been successfully applied for selective control of dissociation products in HI and IBr [36][37][38] and it is also our purpose in this paper to extend this approach to selective control of HOD photodissociation using CW lasers and to explore if we can supplant FOIST-based mixing of vibrational states with much easier mixing of laser colours.…”

A simplification of selective control using field optimized initial state with application to HI and IBr photodissociation

“…The critical role played by the initial vibrational state of the molecule in the product selectivity and yield has motivated our development of a field optimized initial state ͑FOIST͒-based approach to the control of photodissociation reactions. [22][23][24][25][26][27] In this FOIST-based procedure, the control of photodissociation reactions is through the design of an optimal linear combination of a few selected vibrational states prior to the application of the photolysis pulse whose attributes may be chosen for ease of experimental realization. The optimal linear combination from the FOIST procedure achieves selective flux maximization by mixing excited vibrational states to suitably alter the spatial profile of the initial state to facilitate Franck-Condon transition to appropriate region of the excited electronic state͑s͒.…”

“…These optimal linear combinations are field and channel specific and analysis of the FOIST scheme for IBr and HI molecules has been presented earlier. [22][23][24][25][26][27] Initial applications of the FOIST scheme have however utilized a linear combination of the ground and first two excited vibrational states (vϭ0, 1, and 2, respectively͒ requiring a complex fundamental plus overtone excitation, making the experimental realization of these optimal initial states somewhat difficult. Also, the photolysis field ⑀(t) ϭA ͚ pϭ0 2 cos(Ϫ p,0 )t with ប p,0 ϭE p ϪE 0 utilized in these initial applications consists of a principal frequency and another two colors separated by vibrational frequency difference between vϭ0 (E 0 ) and vϭ1 (E 1 ) and vϭ0 and v ϭ2 (E 2 ).…”

“…The additional frequencies Ϫ 10 and Ϫ 20 provide for molecules in the vibrational levels vϭ1 and v ϭ2 to be transferred to the same final state as those in v ϭ0 under the influence of radiation with frequency . This permits a coherent interference between these different paths to the same final state enhancing selectivity and yield, [22][23][24][25][26][27] but the need for a multicolor photolysis field also adds to the complication of the FOIST scheme. The range of field parameters sampled in these initial applications [22][23][24][25][26][27] has also been somewhat limited.…”