The influence of geometry on the vibronic spectra of quantum aggregates

Eisfeld, Alexander; Schulz, Georg; Briggs, J S

doi:10.1016/j.jlumin.2011.06.043

Cited by 4 publications

(3 citation statements)

References 53 publications

(77 reference statements)

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“…The LD r spectra reveal that the absorbance is essentially isotropic rather than strongly polarized at energies greater than 18 200 cm –1 . Thus, these transitions are likely the result of highly localized exciton transitions that arise from disorder within the aggregate system. , This disorder causes weaker coupling, which reduces coherence length and leads to higher-energy exciton transitions. ,− Moreover, the disorder causes many different exciton transitions that are localized in different patches of the tubes, creating an isotropic continuum of transitions. , …”

Section: Results and Discussionmentioning

confidence: 99%

Quantifying the Polarization of Exciton Transitions in Double-Walled Nanotubular J-Aggregates

2013

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A fully consistent model for the exciton band structure of double-walled 3,3′-bis(2-sulfopropyl)-5,5′,6,6′tetrachloro-1,1′-dioctylbenzimidacarbocyanine (C8S3) J-aggregates was developed using reduced linear dichroism (LD r ) spectroscopy on flow aligned samples. Chemical oxidation was utilized to "turn off"outer wall optical absorption and produce stable aggregate samples with a simplified absorption profile associated only with the nanotube inner wall. The oxidized aggregates were aligned in a flow cell to collect LD r spectra; these spectra reveal a series of both polarized and isotropic transitions. Four spectral transitions, assigned to be purely parallel or perpendicular to the aggregate long axis, that fit both the experimental LD r and isotropic spectra were used create a model for oxidized J-aggregate excitonic absorption. The LD r spectral study was repeated using pristine J-aggregates, and the spectrum for the full double-walled J-aggregates could be fit using six total transitions: four from the oxidized fit and two additional transitions distinct to the outer wall. A quantitative model that agrees with experimental absorption and emission spectral results and aligns with current theory was constructed wherein the energies and polarizations of excitonic transitions remained consistent for both the unperturbed and chemically oxidized C8S3 Jaggregates. The polarization studies also reveal, in contrast to the strongly polarized transitions that comprise the low-energy region of the excitonic aggregate spectrum, that the high-energy absorption is unpolarized and attributed to highly localized exciton transitions that arise due to disorder.

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Section: Results and Discussionmentioning

confidence: 99%

Quantifying the Polarization of Exciton Transitions in Double-Walled Nanotubular J-Aggregates

2013

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“…These states possess an oscillator strength that can be considerably enhanced compared to that of a monomer. This enhancement depends essentially on the number of monomers over which the aggregate wave function is coherently delocalized and on the geometrical arrangement of the monomers. ,− In the extreme case the fluorescence lifetime can become N times shorter than that of the monomer, τ fl = τ fl mon / N , where N is the number of monomers. This means that for constant τ nr the quantum yield increases.…”

Section: Theoretical Description and Resultsmentioning

confidence: 99%

Tuning Nonradiative Lifetimes via Molecular Aggregation

Celestino

Eisfeld

2017

J. Phys. Chem. A

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We show that molecular aggregation can strongly influence the nonradiative decay (NRD) lifetime of an electronic excitation. As a demonstrative example, we consider a transition-dipole-dipole-interacting dimer whose monomers have harmonic potential energy surfaces (PESs). Depending on the position of the NRD channel (q), we find that the NRD lifetime (τ) can exhibit a completely different dependence on the intermolecular-interaction strength. We observe that (i) for q near the Franck-Condon region, τ increases with the interaction strength; (ii) for q near the minimum of the monomer excited PES, the intermolecular interaction has little influence on τ; and (iii) for q near the classical turning point of the monomer nuclear dynamics, on the other side of the minimum, τ decreases with the interaction strength. Our findings suggest design principles for molecular systems where a specific fluorescence quantum yield is desired.

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“…The quantum behavior of extended aggregates of atomic and molecular monomers, containing from a just a few up to thousands of subunits, is attracting increasing attention in chemistry and physics, being that proeminent examples are aggregates of large dye molecules, chromophore assemblies describing the photosynthetic unit of assemblies of ultra-cold atoms [ 181 ].…”

Section: Aggregation Of Photosensitizers and Its Influence In Pdtmentioning

confidence: 99%