Sodium azide (NaN3) (99.99+%; Sigma-Aldrich) in D2O (99.9%; Cambridge Isotope Laboratories, Inc.) samples were used to benchmark the performance of the BoxCARS implementation against the pump-probe geometry. All chemicals were used as received. The sample concentration was 50 mM and the spectra were collected at room temperature. The absorbance of the azide asymmetric stretching mode at 2043 cm -1 was measured to be 0.5 OD in the sample used for 2D IR. Spectra were collected in both BoxCARS and pump-probe geometries by scanning the coherence time (t1) from 0 to 4 ps in steps of 20 fs. To reduce any shifting the relative phase between two adjacent pump pulse pairs by π, and the adjacent "0 0" and "0 π" pulse pairs are subtracted and the 2D IR signal is recovered . The waiting times (t2) were select delays from 300 fs to 3 ps as discussed below. The rotating frame frequency was set to 1800 cm -1 . The excitation (ω1) axis was generated by a numerical Fourier-transform along the t1 delay time axis. The interference between the signal and local oscillator was measured in the frequency domain to generate the detection (ω3) axis. Spectra were collected with all pulses in a parallel polarization geometry. Individual spectra were averaged over 50,000 laser shots and collected in five successive sets, then each spectrum was individually phased and summed together to generate the final spectrum at each waiting time.