Two-dimensional infrared spectroscopy (2D IR) is a third-order nonlinear vibrational spectroscopy which provides bond-specific structure and sub-picosecond dynamics of molecules in the condensed phase . Multidimensional spectra contain a wealth of structural information that is derived from the coupling between vibrational modes, producing characteristic spectral lineshapes. Dynamical information on sub-picosecond time scales, such as hydrogen-bonding lifetimes, solvent exchange rates, and conformational dynamics, are extracted from the evolution of the lineshapes as function of waiting time . Two common implementations of 2D IR spectroscopy are based on the four-wave mixing "BoxCARS" and "pump-probe" geometries (Figure ) . While the signals measured in the two geometries, are in principle, identical, there are practical tradeoffs between the two implementations: in the BoxCARS configuration the signal is emitted in a background-free direction and overlapped with a reference "local oscillator" (LO) pulse for reconstruction of the signal amplitude and phase through spectral interferometry . Signal-to-noise ratios (SNRs) are generally higher in the BoxCARS geometry compared to the pump-probe geometry, because the k3 intensity can be adjusted arbitrarily, whereas in the pump-probe geometry k3 also acts as an LO, and its intensity is therefore limited by the dynamic range of the detector.