, and ω2 = 500 cm -1 . The simulations are performed at 300 K, within the bounds of the high temperature approximation, and the Markovian limit Γ max = 2 000 cm -1 . The HEOM simulations for the ODR, IDR, and UDR models contain 1 264, 39 149, and 98 513 ADOs respectively. 2D spectra are generated with a coherence time up to τ = 200 fs in steps of 0.5 fs, for population times of T = 0, 100 and 200 fs.