Photophysics of delocalized excitons in carbazole dendrimers.

The photophysical properties in solution of three generations of carbazole-based dendrons and dendrimers with fluorenyl surface groups were studied using steady-state, time-resolved femtosecond transient absorption and anisotropy, and coherent two-dimensional ultraviolet spectroscopy. It was found that increasing the generation caused a switch in the nature of the emissive state between the first-generation compounds and the second- and third-generation dendrimers. Time-resolved anisotropy measurements revealed low initial anisotropies that decreased with increasing dendrimer generation consistent with increasing intradendrimer interchromophore coupling. Two-dimensional UV spectroscopy showed that the signal from the second- and third-generation dendrimers is the product of multiple chromophores interacting. The maximum number of interacting chromophores is reached by the second generation.

Similarities and differences in the optical response of perylene-based hetero-bichromophores and their monomeric units.

The linear and nonlinear optical response of molecular hetero-dimers and their composing perylene units is explored with fluorometry, steady-state and transient absorption, and coherent two-dimensional electronic spectroscopy. Supported by a Förster theory approach and ab initio calculations, we disclose the photoinduced dynamics comprising excitonic coupling, conformational changes, charge transfer, and relaxation dynamics. The influence of the actual orientation of the two chromophore units on these processes is investigated by employing two bichromophores built of the same monomeric units but linked differently.

Coherent two-dimensional ultraviolet spectroscopy in fully noncollinear geometry.

We introduce fully noncollinear coherent two-dimensional (2D) spectroscopy in the UV domain with an all-reflective and miniaturized setup design. Phase stability is achieved via pairwise beam manipulation, and the concept can be transferred to all wavelength regimes. Here we present results from an implementation that has been optimized for wavelengths between 250 and 375 nm. Interferometric measurements prove phase stability over several hours. We obtained 2D spectra of the nonpolar UV chromophore p-terphenyl in ethanol, excited with 50 fs pulses at 287 nm.

Inherently phase-stable coherent two-dimensional spectroscopy using only conventional optics.

We introduce an inherently phase-stable setup for coherent two-dimensional femtosecond spectroscopy in noncollinear box geometry using only conventional beam splitters, mirrors, and delay stages. Avoiding diffractive optics, pulse shapers, and active phase-locking loops, our spectroscopy setup is simple, robust, and works for ultrabroad bandwidths in all spectral regimes (infrared, visible, and ultraviolet).