Model Calculations on Laser Induced Dissociation of Bromine with Control of Electronic Product Excitation

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Abstract
After a short survey of different methods to control electronic product excitations in laser‐induced unimolecular dissociations we develop an alternative strategy, adapted to interfering exit channels with potential energy curve crossings, and implement it for the bromine system. In a reference case with zero potential couplings optimal initial population of the competing dissociative states leads to complete product selectivity. In the real system, however, the electronically excited molecules pass the potential energy curve crossing of the B 3Πo + u and 1Π1u states on their way to dissociation, and Landau‐Zener‐type diabatic transitions establish the final product distribution. For this case we discuss the possibility to refine the electronic product distribution by a second, intense laser pulse applied after the curve crossing. Based on these results inversion of experimental product distribution data may be used to determine the curve crossing parameters, thus extending the short range information obtained from Raman scattering. Simulation of laser controlled dissociation is achieved by FFT (fast Fourier transform) propagation of representative wave packets.

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