Optical line shapes of dynamically disordered ring aggregates

Abstract

We study the absorption line shape caused by Frenkel excitons in one-dimensional ring-shaped molecular aggregates, such as circular light-harvesting systems, subjected to dynamic disorder with a finite correlation time. We focus on dichotomic noise and show that for arbitrary orientations of the molecular transition dipoles relative to the ring, the absorption spectrum may be calculated exactly by solving two very similar sets of 2N coupled linear equations of motion, where N is the number of molecules in the ring. These sets are a factor of N smaller than in methods developed previously, which allows us to evaluate the exact line shapes for N up to 12 and study size dependence of the spectra. Previous exact calculations were limited to hexamers (N=6). Moreover, in contrast to earlier work, we take into account long-range dipolar transfer interactions between all molecules in the ring. We find that the dipole orientation and the long-range interactions strongly affect the dependence of the spectrum on the ring size. This holds true particularly for the exchange narrowing of the linewidths in the fast-fluctuation regime.

Polarized absorption and anomalous temperature dependence of fluorescence depolarization in cylindrical J-aggregates

“…For the higher-energy (k ¼ AE1) absorption line, the narrowing factor is less than for the k ¼ 0 state, as a consequence of the disorder-induced splitting within the degenerate pair. In the case of fast dynamic energy disorder, it has been shown that the higher-energy (k ¼ AE1) line is twice as broad as the low-energy (k ¼ 0) one [23], while in the case of static energy disorder, the difference is a factor of ffiffi ffi 2 p [24]. Moreover, the higher line is also broadened by energy relaxation to the lower state.…”

Pigment–protein architecture in the light‐harvesting antenna complexes of purple bacteria: does the crystal structure reflect the native pigment–protein arrangement?

“…The predicted excitation level structure [6,10–13] of the lowest‐energetic one‐excitation band of an 18 BChls a numbered, completely ordered circular aggregate (i.e. identical Q y excitation energy of the individual BChls a ) of C 9 symmetry is shown in Fig.…”

Influence of energy transfer on the intensity pattern of vibronic excitation studied by reduced density-matrix theory

“…Molecular aggregates including photosynthetic [1][2][3][4][5][6][7][8] and other biological pigment-protein complexes [9][10][11] and optoelectronic devices [12][13][14] have been extensively investigated by using spectroscopic methods and theories [15][16][17][18][19][20][21][22][23]. In such aggregates, monomeric molecular units are electronically coupled to each other to produce a collective spectral properties such as line narrowing, super-radiance, and coherent or incoherent excitation energy transfer.…”