Pulse Overlap Artifacts in Action-Detected One-Dimensional and Two-Dimensional Electronic Spectroscopy

Action-detected multidimensional electronic spectroscopy has become a powerful tool for probing excited-state dynamics because of its intrinsic phase stability and direct sensitivity to fluorescence or photocurrent signals. However, its reliability critically relies on phase-cycling schemes that assume complete temporal separation between excitation pulses. In practical experiments employing femtosecond laser pulses, temporal pulse overlap is often unavoidable and may introduce spurious spectral features that complicate data interpretation. Here, we present a systematic theoretical investigation of pulse-overlap artifacts in action-detected one-dimensional (1D) and two-dimensional (2D) electronic spectroscopy based on Lindblad quantum master equation simulations. We show that pulse overlap breaks the discrete-phase assumption underlying conventional phase cycling, resulting in signal leakage and pathway mixing among different nonlinear channels. In two-pulse 1D spectroscopy, pulse overlap generates artificial high-order spectral components that can be completely eliminated through appropriate phase cycling. In four-pulse 2D spectroscopy, we identify two distinct artifact regimes associated with intrapair and interpair pulse overlap that persist even after phase cycling, leading respectively to cross-talk between rephasing and nonrephasing signals and to contamination of the two-quantum coherence channel. Quantitative analysis reveals that artifact amplitudes follow an approximately Gaussian evolution governed by the pulse-overlap integral, whereas deviations near zero delay arise from cooperative multipulse overlap and high-order nonlinear responses. These results establish a unified physical framework for understanding pulse-overlap artifacts in action-detected multidimensional spectroscopy and provide practical guidelines for their identification, interpretation, and suppression in ultrafast spectroscopic experiments.