Theoretical Study on Exciton Recurrence Motion in Anthracene Dimer Using the Ab Initio MO-CI Based Quantum Master Equation Approach

Abstract

We apply the ab initio molecular orbital (MO)-configuration interaction (CI) based quantum master equation (MOQME) method to the investigation of ultrafast exciton dynamics in an anthracene dimer modeled after anthracenophane, which is experimentally found to exhibit an oscillatory signal of fluorescence anisotropy decay. Two low-lying near-degenerate one-photon allowed excited states with a slight energy difference (42 cm(-1)) are obtained at the CIS/6-31G** level of approximation using full valence pi-orbitals. The time evolution of reduced exciton density matrices is performed by numerically solving the quantum master equation. After the creation of a superposition state of these near-degenerate states by irradiating a near-resonant laser field, we observe two kinds of oscillatory behaviors of polarizations: field-induced polarizations with faster periods, and amplitude oscillations of x- and z-polarizations, P(x) and P(z), with a slower period, in which the amplitudes of P(x) and P(z) attain maximum alternately. The latter behavior turns out to be associated with an oscillatory exciton motion between the two monomers, i.e., exciton recurrence motion, using the dynamic exciton expression based on the polarization density. From the analysis of contribution to the exciton distributions, such exciton recurrence motion is found to be characterized by both the difference in eigenfrequencies between the two near-degenerate states excited by the laser field and the relative phases among the frontier MOs primarily contributing to the near-degenerate states.

Open-Shell-Character-Based Molecular Design Principles: Applications to Nonlinear Optics and Singlet Fission

“…The clarification of the relationship between the diradical character and vibronic coupling will contribute to opening a new path to constructing design and control guidelines for a variety of dynamic functionalities related to the excited states. In such fields, considering the high stimuli responsiveness of open‐shell molecular systems, the investigation of the dissipative quantum dynamics with “open quantum system approaches” should also be important to further understanding as well as designing the dynamic functionality, which is another research topic of my studies . Thus, the rational design of “open quantum systems” composed of “open‐shell molecular systems” interacting with environments (reservoirs) together with the reservoir design (Figure ) will be challenging targets in the future, though they could not be described in this account due to limitations of space.…”

Calculations of nonlinear wave-packet interferometry signals in the pump-probe limit as tests for vibrational control over electronic excitation transfer

“…Next we examine excitation-transfer dynamics and pump-probe signals from an EET complex with parameter values appropriate to dithia-anthracenophane ͑DTA͒, a covalent anthracene dimer compound that has been studied by Yamazaki et al 47,48 using time-resolved pump-probe anisotropy measurements. Two vibrational modes of the anthracene monomer, mode-12 at 12 / 2c = 385 cm −1 and mode-6 at 6 / 2c Х 1400 cm −1 , dominate the vibronic progression of its S 1 ← S 0 fluorescence-excitation spectrum within 1500 cm −1 of its origin at 27 695 cm −1 .…”

“…We use an effective energy-transfer coupling constant J = ͑33.6 cm −1 / 2͒exp͑␦ 12 2 ͒ = 0.0595 12 = 22.9 cm −1 obtained by dividing half the population-oscillation frequency reported in Ref. 48 by the estimated Franck-Condon overlap between two mode-12 wave packets separated by their relative displacement ͑ ͱ 2d 12 ͒ in the two site-excited potential wells. 50 The two anthracene-monomer transitiondipole moments in DTA are known to be approximately, but not exactly, orthogonal; 47 for simplicity, their relative angle is set to ␣ = / 2 in our calculations.…”

Theoretical Study on Exciton Dynamics in Dendritic Systems: Exciton Recurrence and Migration

“…On the other hand, the coherent dynamics of exciton or electron in super- and supra-molecules have been intensively investigated toward a fundamental understanding of dynamics of excited states and a new development of molecular-based nano-scale devices [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. The coherent excitation by irradiation of laser fields creates superposition states composed of plural excited states, which cause the spatial oscillation of excitation, i.e., exciton recurrence motion.…”

“…have observed the oscillatory anisotropy decay for anthracene dimer, i.e., dithiaanthracenophane (DTA) in solution, which is longer than that for BN [ 42 , 43 , 44 ]. Theoretical studies on the mechanism of these phenomena have been performed using the quantum master equation (QME) approach using the dipole coupled aggregate models [ 45 , 46 ] and ab initio MO configuration interaction (CI) based QME (MOQME) approach [ 47 , 48 ]. It has been found from these results that the rigid and fixed molecular structure plays an important role in reducing the dephasing rate [ 30 ].…”