Simulations of two-dimensional femtosecond infrared photon echoes of glycine dipeptide

The multidimensional optical response of the amide I band of glycine dipeptide is calculated using a vibrational-exciton model, treating each peptide bond as a localized anharmonic vibration. The 2D photon echo signal is obtained by solving the non-linear exciton equations. Comparison of different models of spectral broadening (homogeneous and diagonal and off-diagonal static disorder) shows completely different 2D signals even when the 1D infrared spectra are very similar. The phase of the 2D signal may be used to distinguish between overtone and collective types of two-exciton states. Vanishing of the 2D signal along certain directions can be attributed to the variation of the phase. Copyright (C) 2000 John Wiley and Sons, Ltd.