David Coker

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Modeling non-perturbative field-driven vibronic dynamics: Selective state preparation and nonlinear spectroscopy

Ultrafast Electromagnetic fields that can be shaped in time and frequency may be employed to selectively control photo excited vibrational wave packet dynamics in different molecular electronic states. In principle this idea can be used, for example, to steer photo excited molecules through conical intersections to manipulate branching between internal conversion and excited state energy transfer relaxation pathways, and other photo excited control scenarios. We have recently extended the partially linearized density matrix approach for non-adiabatic excited state dynamics to incorporate an arbitrary classical external electromagentic field into the system Hamiltonian enabling the treatment of direct field-driven quantum dynamics and the computation of a variety of linear and nonlinear spectroscopic signals beyond the perturbative limit of standard response function theory. In this talk we explore the capabilities of the approach with a simple two-state vibronic model coupled to a bath, for which we (a) perform an exhaustive search in the field parameter space for optimal state preparation and (b) compute time-resolved transient absorption spectroscopy to monitor the effect of different pulse shapes on measurable experimental signals. While no restrictions on the form of the field are assumed, we focus here on Gaussian shaped (linearly) chirped pulses.