Abstract
In a seminal work the photodissociation of IBr has been controlled using a strong non-resonant IR pulse [Sussman et al., Science, 2006, 314, 274], changing the branching ratio of products in different final states via the relative timing of pump and control pulses. In this paper, we revisit the control of this molecule. Potential surfaces for the complete spin-orbit manifold of IBr states dissociating into the ground and first excited states of the constituent atoms have been calculated at the multi-reference configuration interaction (MRCI) level of theory as a function of applied field. Both the strength and direction of field have been taken into account and it is seen how the avoided crossing between the states thought to be key in the control mechanism shift as a function of field strength. These surfaces will enable full calculations of the molecule in the pump-control field. Preliminary dynamics calculations with the field placed along the molecular axis show that a Hamiltonian including all 36-states agrees with earlier results and is able to model the basic features of the control. However, just like earlier results, this restricted model is not able to reproduce the timescale of the control.
Highlights
The strong-field control of the photodissociation of IBr by Stolow and co-workers[1,2] is a classic example of affecting the outcome of a chemical reaction by modifying the potential curves near a curve crossing using the non-resonant dynamic Stark effect
The field strength and angle of the electric field are specified in each plot
The grid used for all propagations presented in this paper is a Fast Fourier Transform (FFT) collocation, with a total of 256 points running from interatomic distances between 4.0 and 12.00 Bohr
Summary
The strong-field control of the photodissociation of IBr by Stolow and co-workers[1,2] is a classic example of affecting the outcome of a chemical reaction by modifying the potential curves near a curve crossing using the non-resonant dynamic Stark effect. The timescale for the control is much shorter in the simulations, with the simulations showing that the photodissociation reaction is over in around 100 fs while the experiments show a control effect out to 500 fs.[1,3] To understand the origin of this discrepancy it is first necessary to build a complete and accurate theoretical description of IBr able to reproduce the experimental data. Comparison of this full description and the models used previously will provide the missing link
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