Pump–probe spectrum of molecular assemblies of arbitrary structure and dimension

Abstract

Multidimensional femtosecond spectroscopies of molecular aggregates and semiconductor nanostructures: The nonlinear exciton equations Using the hard-core boson approach, we study the pump-probe spectrum of molecular assemblies carrying Frenkel excitons of arbitrary structure and dimension. We present a rigorous justification of the hard-core boson approach by using the Agranovich-Toshich transformation from paulions to bosons. The resulting two-exciton Green function is used to derive a general expression of the assembly's pump-probe spectrum. We show that this expression considerably simplifies for ordered systems occupying a lattice, where we allow for the occurrence of more than one equivalent molecule in the unit cell ͑Davydov components͒. Explicit semianalytical expressions are given for the pump-probe spectrum of linear chains with alternating dipoles, ring aggregates, chains with a herringbone structure, and monolayers. In the analysis of these expressions, we focus on the overall shape of the spectrum and on the effects of probe polarization. It is shown that relaxation during the pump-probe delay time may drastically affect the pump-probe spectrum.

Investigation of structure–spectroscopy–function relationship of two-dimensional J-aggregates of tetrachlorobenzimidazolocarbocyanine preferentially oriented in poly-vinyl-alcohol thin films

“…4, the peak positions are on the red/at the bottom of both bands for V J (1) < 0, V J-J (1) > 0, and V J-J (2) < 0 and are located at [31] E J ðmaxÞ ¼ E 0 þ 2V J ð1Þ À ½V JÀJ ð1Þ þ 2V JÀJ ð2Þ ð2aÞ The transition dipole moments corresponding to the H-and the J-peaks are polarized, respectively, along the aggregate axis and perpendicular to it and have the isotropic absorbance ratio of f(a) = A iso,H /A iso,J = cot g 2 a. For finite inhomogeneous aggregates a redistribution of the peak intensities into a band of transitions and some intensity borrowing between the two bands will be exhibited.…”

Exciton Level Structure and Dynamics in Tubular Porphyrin Aggregates

“…50 We generalized the method of ref. 49 in order to treat the case with several electronic excited states per molecule. To make the calculations feasible, we neglected (only in these calculations) the coupling to vibrations as well as the effects of static disorder, the details are given in section II of the SI.…”

“…Pump-probe spectrum: we modeled this using the hard-core boson approach, which does not require calculating the two-exciton states; the latter would make it impossible to model systems as large as these porphyrin nanotubes [48][49] Previously, the method has been applied to tubular aggregates with one transition per molecule. 50 We generalized the method of ref.…”

Polarized absorption spectra of highly oriented two-dimensional aggregates of tetrachlorobenzimidazolocarbocyanine in thin films

“…Next we shall discuss that the polarized absorption spectra are compatible with the herringbone model, in which the polarizations of the H-and J-bands are, respectively, along the aggregate axis and perpendicular to the aggregate axis for the homogeneous infinite aggregates [7]. These assignments for the polarization directions hold to a good approximation for the inhomogeneous finite aggregates [8].…”

“…This analysis was based on the simulations of the A iso in the Frenkel exciton formalism [5][6][7][8][9] and on the discussion of the fluorescence excitation and emission data. A typical simulation is shown and is detailed in Fig.…”