Surface hopping modeling of two-dimensional spectra.

Recently, two-dimensional (2D) electronic spectroscopy has become an important tool to unravel the excited state properties of complex molecular assemblies, such as biological light harvesting systems. In this work, we propose a method for simulating 2D electronic spectra based on a surface hopping approach. This approach self-consistently describes the interaction between photoactive chromophores and the environment, which allows us to reproduce a spectrally observable dynamic Stokes shift. Through an application to a dimer, the method is shown to also account for correct thermal equilibration of quantum populations, something that is of great importance for processes in the electronic domain. The resulting 2D spectra are found to nicely agree with hierarchy of equations of motion calculations. Contrary to the latter, our method is unrestricted in describing the interaction between the chromophores and the environment, and we expect it to be applicable to a wide variety of molecular systems.