title: Disentangling electronic and vibronic coherences in two-dimensional echo spectra.
abstract: The prevalence of long-lasting oscillatory signals in two-dimensional (2D) echo spectroscopy of light-harvesting complexes has led to a search for possible mechanisms. We investigate how two causes of oscillatory signals are intertwined: (i) electronic coherences supporting delocalized wavelike motion and (ii) narrow bands in the vibronic spectral density. To disentangle the vibronic and electronic contributions, we introduce a time-windowed Fourier transform of the signal amplitude. We find that 2D spectra can be dominated by excitations of pathways which are absent in excitonic energy transport. This leads to an underestimation of the lifetime of electronic coherences by 2D spectra.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA.
authors.forename: Christoph
authors.initials: C
authors.lastname: Kreisbeck
authors.forename: Tobias
authors.initials: T
authors.lastname: Kramer
authors.forename: Alán
authors.initials: A
authors.lastname: Aspuru-Guzik
mesh_terms: D004583:Electrons; D005583:Fourier Analysis; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D014732:Vibration
chemical_list: D045342:Light-Harvesting Protein Complexes