Pulse overlap ambiguities in multiple quantum coherence spectroscopy

Coherent two-dimensional electronic spectroscopy probes ultrafast dynamics using femtosecond pulses. In case the timescale of the studied dynamics become comparable to the pulse duration, pulse overlap effects may compromise the experimental data. Here, we perform one-dimensional coherence scans and study pulse overlap effects in clean two-level systems. We find parasitic multiple-quantum coherence signals as a consequence of the arbitrary time ordering during the temporal pulse overlap. Surprisingly, the signal lifetimes exceed the temporal pulse overlap by a factor of 1.8. These findings have important implications for the interpretation of higher-order coherent two-dimensional and related spectroscopy experiments.