Two-dimensional time-frequency ultrafast infrared vibrational echo spectroscopy

2D spectrally resolved ultrafast (< 200 fs) IR vibrational echo experiments were performed on Rh(CO)(2)acac [(acetylacetonato)dicarbonylrhodium (I)]. The 2D spectra display features that reflect the 0-1 and 1-2 transitions an d the combination band transition of the symmetric (S) and antisymmetric (A ) CO stretching modes. Three oscillations in the data arise from the freque ncy difference between the S and A modes (quantum beats) and the,C and A an harmonicities. A new explanation is given for these "anharmonic" oscillatio ns. Calculations show that spectral resolution enables the 0-1 and 1-2 deph asing to be measured independently.