Theoretical Prediction of the 2-Dimensional Electronic Spectrum of Different Simulation Models of the Hydrated Electron

Linear absorption spectroscopy has been the workhorse experimental method for probing hydrated electrons for the last several decades. There has been essentially no work, however, characterizing the nonlinear spectroscopy, such as the 2-dimensional electronic spectrum (2DES), of this species, despite the wealth of additional information that the 2DES provides. Nonlinear spectroscopy can directly measure homogeneous and inhomogeneous linewidths, quantify spectral diffusion, and probe the characteristic solvent dynamics that drive temporal line-shape evolution. This is particularly attractive for studying different simulation models of the hydrated electron. Most such models produce a roughly spherical charge density that predict a linear absorption spectrum in reasonable agreement with experiment, even though the solvent structure and dynamical fluctuations underlying these models are quite different. Thus, the temporal evolution of the 2DES signal provides an experimentally verifiable means to discriminate between different models and levels of theory for this species. In this work, we present the first theoretical predictions of the hydrated electron's 2DES. We show that two different one-electron models that produce very similar linear absorption spectra display distinct temporal dynamics of their 2DES signals. The results function not only as a prediction that can be compared directly to future experiments but also illustrate the utility of nonlinear spectroscopy in understanding the solvation dynamics of fully solvent-supported hydrated electron systems.