Comparison of Electronic and Vibrational Coherence Measured by Two-Dimensional Electronic Spectroscopy

The short pulse durations and broad frequency spectra of femtosecond laser pulses allow coherent superpositions of states to be prepared and probed. Two-dimensional electronic spectroscopy (2D ES) has the potential to identify more clearly the origin and evolution of such coherences. In this report we examine how electronic and vibrational coherences can be distinguished by decomposing the total 2D ES signal into rephasing and nonrephasing components. We investigate and identify differences between the cross peak oscillations measured in two laser dyes with those measured in the PC645 light-harvesting antenna protein of the cryptophyte alga Chroomonas sp. strain CCMP270 at ambient temperature.