title: Electronic Double-Quantum Coherences and Their Impact on Ultrafast Spectroscopy: The Example of β-Carotene.
abstract: The energy level structure and dynamics of biomolecules are important for understanding their photoinduced function. In particular, the role of carotenoids in light-harvesting is heavily studied, yet not fully understood. The conventional approach to investigate these processes involves analysis of the third-order optical polarization in one spectral dimension. Here, we record two-dimensional correlation spectra for different time-orderings to characterize all components of the transient molecular polarization and the optical signal. Single- and double-quantum two-dimensional experiments provide insight into the energy level structure as well as the ultrafast dynamics of solvated β-carotene. By analysis of the lineshapes, we obtain the transition energy and characterize the potential energy surfaces of the involved states. We obtain direct experimental proof for an excited state absorption transition in the visible (S2→Sn2). The signatures of this transition in pump-probe transients are shown to lead to strongly damped oscillations with characteristic pump and probe frequency dependence.
authors.affiliation: Faculty of Physics, University of Vienna, Strudlhofgasse 4, 1090 Vienna, Austria.
authors.forename: Niklas
authors.initials: N
authors.lastname: Christensson
authors.forename: Franz
authors.initials: F
authors.lastname: Milota
authors.forename: Alexandra
authors.initials: A
authors.lastname: Nemeth
authors.forename: Igor
authors.initials: I
authors.lastname: Pugliesi
authors.forename: Eberhard
authors.initials: E
authors.lastname: Riedle
authors.forename: Jaroslaw
authors.initials: J
authors.lastname: Sperling
authors.forename: Tõnu
authors.initials: T
authors.lastname: Pullerits
authors.forename: Harald F
authors.initials: HF
authors.lastname: Kauffmann
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hauer