Two-dimensional spectroscopy beyond the perturbative limit: The influence of finite pulses and detection modes

Abstract

Ultra-fast and multi-dimensional spectroscopy gives a powerful looking glass into the dynamics of molecular systems. In particular, two-dimensional electronic spectroscopy (2DES) provides a probe of coherence and the flow of energy within quantum systems, which is not possible with more conventional techniques. While heterodyne-detected (HD) 2DES is increasingly common, more recently fluorescence-detected (FD) 2DES offers new opportunities, including single-molecule experiments. However, in both techniques, it can be difficult to unambiguously identify the pathways that dominate the signal. Therefore, the use of numerically modeling of 2DES is vitally important, which, in turn, requires approximating the pulsing scheme to some degree. Here, we employ non-perturbative time evolution to investigate the effects of finite pulse width and amplitude on 2DES signals. In doing so, we identify key differences in the response of HD and FD detection schemes, as well as the regions of parameter space where the signal is obscured by unwanted artifacts in either technique. Mapping out parameter space in this way provides a guide to choosing experimental conditions and also shows in which limits the usual theoretical approximations work well and in which limits more sophisticated approaches are required.

Higher-Order Multidimensional and Pump–Probe Spectroscopies

“…There are two main routes to simulating such spectra. In nonperturbative simulations, the system evolves in time due to both its native propagation and its interaction with the optical pulses, where phase matching is simulated either with a spatially distributed set of systems or by a phase-cycling procedure. ,− Such simulations, as their name indicates, inherently include higher-order effects of the optical pulses and thus are not designed to extract the separate perturbative orders of the response of a system. But such an extraction could be performed using the same techniques described here and in our earlier publication by calculating either several intensity-dependent PP simulations or windowed integration of separated n Q signals …”

Equation-of-Motion Methods for the Calculation of Femtosecond Time-Resolved 4-Wave-Mixing and N-Wave-Mixing Signals

“…These are the signatures of strong system–field coupling. Related questions were recently studied in refs and .…”

Simulating action-2D electronic spectroscopy of quantum dots: insights on the exciton and biexciton interplay from detection-mode and time-gating

“…Our simulation protocol, described in Section 2, is based on a non-perturbative approach to the light–matter interaction and it directly implements the phase-modulation scheme in close analogy with the experimental procedure. 43 Besides the advantage of accounting for finite-bandwidth and pulse-overlap effects, 44 it allows a flexible description of different relaxation pathways through the modeling of the dissipator of a Quantum Master Equation (QME) in the Lindblad form. This setting will allow us to naturally include the slow incoherent processes involved in the action-detection scheme in the simulation of the spectra.…”