Field-Optimized Initial State-Based Selective Control of IBr Photodissociation

Abstract

A new scheme for controlling photodissociation through preparation of a variationally optimized linear superposition of field-free vibrational eigenstates is applied for selective control of IBr photodissociation. The dependence of IBr photodissociation on various field parameters and initial conditions is explored. In a broad range of field parameters, the product yield is shown to increase considerably when a photolysis pulse is applied to the variationally optimized linear combination as opposed to photolysis of IBr with the entire population in a single vibrational level. The frequency, intensity, and phase dependence of this enhancement is explored for both CW and Gaussian pulses.

Photodynamic control using field optimized initial state: A mechanistic investigation of selective control with application to IBr and HI photodissociation

“…Since the initial vibrational state which is subjected to photolysis is critical in determining the photodissociation products, it is reasonable to expect an appropriately optimized linear superposition of these vibrational eigenstates to serve as a better initial condition for selective maximization of the desired product. Towards this end, a scheme to establish the optimal linear mix of the field free vibrational eigenstates for the given photolysis pulse and chosen photodissociation objective has been pursued in our group 20,21 whereby, the emphasis is shifted from control through design of an appropriate field, to control through the design of an optimal linear combination of the field free vibrational eigenstates for the chosen photolysis pulse. Applications of field optimized initial state ͑FOIST͒ based selective control to HI 20 and IBr 21 have successfully identified the optimal linear combinations for multicolor continuous wave ͑cw͒ and Gaussian fields of different intensities, frequencies, and phase differences and considerable enhancement in selectivity and product yield using these field optimized initial states has been demonstrated.…”

“…Towards this end, a scheme to establish the optimal linear mix of the field free vibrational eigenstates for the given photolysis pulse and chosen photodissociation objective has been pursued in our group 20,21 whereby, the emphasis is shifted from control through design of an appropriate field, to control through the design of an optimal linear combination of the field free vibrational eigenstates for the chosen photolysis pulse. Applications of field optimized initial state ͑FOIST͒ based selective control to HI 20 and IBr 21 have successfully identified the optimal linear combinations for multicolor continuous wave ͑cw͒ and Gaussian fields of different intensities, frequencies, and phase differences and considerable enhancement in selectivity and product yield using these field optimized initial states has been demonstrated. 20,21 The optimal combinations depend on the choice of the photodissociation objective, i.e., the linear combination which will maximize flux out of the IϩBr( 2 P 3/2 ) in the IBr differs markedly from that which will maximize flux out of the excited IϩBr*( 2 P 1/2 ) channel.…”

“…Applications of field optimized initial state ͑FOIST͒ based selective control to HI 20 and IBr 21 have successfully identified the optimal linear combinations for multicolor continuous wave ͑cw͒ and Gaussian fields of different intensities, frequencies, and phase differences and considerable enhancement in selectivity and product yield using these field optimized initial states has been demonstrated. 20,21 The optimal combinations depend on the choice of the photodissociation objective, i.e., the linear combination which will maximize flux out of the IϩBr( 2 P 3/2 ) in the IBr differs markedly from that which will maximize flux out of the excited IϩBr*( 2 P 1/2 ) channel. 21 Similar considerations hold in the photodissociation of HI as well.…”

“…20,21 The optimal combinations depend on the choice of the photodissociation objective, i.e., the linear combination which will maximize flux out of the IϩBr( 2 P 3/2 ) in the IBr differs markedly from that which will maximize flux out of the excited IϩBr*( 2 P 1/2 ) channel. 21 Similar considerations hold in the photodissociation of HI as well. 20 The FOIST scheme achieves selective flux maximization by altering the spatial profile of the initial state to be subjected to the photolysis pulse and since changes in flux are due to the flow of probability density, it is our purpose here to analyze the probability density profiles of the optimal superpositions to try and isolate the mechanistic features which may be responsible for selective control.…”

“…b͒ Electronic mail: mmishra@chem.iitb.ernet.in of this article. The results to be discussed are an attempt to search for simplifying features so that the onus for selective control of chemical reactions does not lie entirely on the laser fields which thereby may come out to be complicated 26 but the task of selective control is split into different parts 20,21 which could be comparatively easier to realize in ordinary laboratory conditions.…”