title: Two-dimensional electronic spectra of symmetric dimers: Intermolecular coupling and conformational states.
abstract: We study the information content of two-dimensional (2D) electronic photon-echo (PE) spectra, with special emphasis on their potential to distinguish, for waiting times T=0, between different conformations of electronically coupled symmetric dimers. The analysis is performed on the basis of an analytical formula for the frequency-domain 2D PE signal. The symmetric dimers are modeled in terms of two identical, energy-degenerate, excitonically coupled pairs of electronic states in the site representation. The spectra of conformationally weighted ensembles, composed of either two or four dimers, are compared with their one-dimensional linear absorption counterparts. In order to provide a realistic coupling pattern for the ensemble consisting of four dimers, excitonic couplings are estimated on the basis of optimized geometries and site-transition dipole moments, calculated by standard semiempirical methods for the bridged bithiophene structure 1,2-bithiophene-2-yl-ethane-1,2-dion (T2[CO]2). In the framework of our model, the highly readable 2D PE spectra can unambiguously identify spectral doublets, by relating peak heights and positions with mutual orientations of site-localized transition dipoles.
authors.affiliation: Institute of Chemistry, Comenius University, Mlynská dolina CH2, 842 15 Bratislava, Slovakia. szocs@fns.uniba.sk
authors.forename: V
authors.initials: V
authors.lastname: Szöcs
authors.forename: T
authors.initials: T
authors.lastname: Pálszegi
authors.forename: V
authors.initials: V
authors.lastname: Lukes
authors.forename: J
authors.initials: J
authors.lastname: Sperling
authors.forename: F
authors.initials: F
authors.lastname: Milota
authors.forename: W
authors.initials: W
authors.lastname: Jakubetz
authors.forename: H F
authors.initials: HF
authors.lastname: Kauffmann