Static spectra offer ensemble-averaged structural views of equilibrium conformations. Obtaining Dynamics of local environments surrounding the IR probes can be detected on a sub-picosecond timescale by varying the delay between pump and probe pulses (t2). In 2D IR spectra, peaks are elongated along the diagonal at early waiting time and become rounder at late waiting time as pump and probe frequencies gradually decorrelate due to the frequency fluctuations when ensembles initially excited at a given frequency become randomized. This process is referred to as spectral diffusion. In essence, waiting-time-dependent 2D IR spectra measure the frequency-frequency correlation function (FFCF) of each vibrational probe within the system . The frequency decorrelation times, encoded within the 2D lineshapes, can be extracted using numerical analysis methods such as center line slope , nodal line slope , ellipticity parameter , or fitting to a model response function .