The separation of overlapping transitions in β-carotene with broadband 2D electronic spectroscopy

Broadband 2D electronic spectroscopy is applied to beta-carotene, revealing new insight into the excited state dynamics of carotenoids by exploring the full energetic range encompassing the S-0 -> S-2 and S-1 -> S-1n transitions at 77 K. Multiple signals are observed in the regime associated with the proposed S* state and isolated through separate analysis of rephasing and nonrephasing contributions. Peaks in rephasing pathways display dynamic lineshapes characteristic of coupling to high energy vibrational modes, and simulation with a simple model supports their assignment to impulsive stimulated Raman scattering. A signal persisting beyond 10 ps in the nonrephasing spectra is still under investigation. (C) 2011 Elsevier B.V. All rights reserved.