• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.933-940
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• 2012

Recently, it has been shown that quantum coherence appears in energy transfers of various photosynthetic lightharvesting complexes at from cryogenic to even room temperatures. Because the photosynthetic systems are inherently complex, these findings have subsequently interested many researchers in the field of both experiment and theory. From the theoretical part, simplified dynamics or semiclassical approaches have been widely used. In these approaches, the quantum-classical Liouville equation (QCLE) is the fundamental starting point. Toward the semiclassical scheme, approximations are needed to simplify the equations of motion of various degrees of freedom. Here, we have adopted the Poisson bracket mapping equation (PBME) as an approximate form of QCLE and applied it to find the time evolution of the excitation in a photosynthetic complex from marine algae. The benefit of using PBME is its similarity to conventional Hamiltonian dynamics. Through this, we confirmed the coherent population transfer behaviors in short time domain as previously reported with a more accurate but more time-consuming iterative linearized density matrix approach. However, we find that the site populations do not behave according to the Boltzmann law in the long time limit. We also test the effect of adding spurious high frequency vibrations to the spectral density of the bath, and find that their existence does not alter the dynamics to any significant extent as long as the associated reorganization energy is changed not too drastically. This suggests that adopting classical trajectory based ensembles in semiclassical simulations should not influence the coherence dynamics in any practical manner, even though the classical trajectories often yield spurious high frequency vibrational features in the spectral density.

• Journal of the Optical Society of Korea
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• v.1 no.2
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• pp.94-99
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• 1997

In this paper, we calculate the four coefficients for the quantum theory of multiwave mixing including a local-field correction resulting from dipole-dipole interactions. We make contact with the semiclassical calculations of probe absorption and four-wave-mixing coupling coefficients, and illustrate the effects of local field corrections on resonance-fluorescence and coupled-mode-fluorescence spectra. The method uses the hybrid quantum-Langevin-equation master-equation approach of An and Sargent.

• Journal of the Korean Chemical Society
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• v.22 no.4
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• pp.202-220
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• 1978

Uniform semiclassical (WKB) solutions are obtained for nonseparable systems without using a close coupling formalism and are given explicitly in terms of well known analytic functions for various physically interesting and realistic cases. They do not become singular at turning points or surfaces and when taken in their asymptotic forms, they reduce to the usual WKB solutions that could be obtained if the Stokes phenomenon was properly taken care of for solutions. In obtaining such uniform solutions, the Schroedinger equations for nonseparable systems are suitably "renormalized" to solvable "normal" forms through certain transformations. Ehrenfest's adiabatic principle plays an important guiding role for obtaining such "renormalized" uniform solutions for nonseparable systems. The eigenvalues of the Hamiltonian can be calculated from the extended Bohr-Sommerfeld quantization rules when appropriate classical trajectories are obtained. An application is made to many-electron systems and for one of the simplest examples to show the utility of the method the approximate wavefunction is calculated of the ground state helium atom.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.294-299
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• 2003

We have investigated the structures of copper nanowires encapsulated in carbon nanotubes using a structural optimization process applied to the steepest descent method. The results showed that the stable morphology of the cylindrical ultrathin copper nanowires in carbon nanotubes is multishell packs consisted of coaxial cylindrical shells. As the diameter of copper nanotubes increased, the encapsulated copper nanowires have the face centered cubic structure as the bulk. Both the semiclassical orbits in a circle and the circular rolling of a triangular network can explain the structures of ultrathin multishell copper nanowires encapsulated in carbon nanotubes.

• Bulletin of the Korean Chemical Society
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• v.24 no.6
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• pp.703-711
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• 2003

We have theoretically studied the nonadiabatic transitions among the five lower states with the Ω=$1_u$ symmetry ($1_u^{(1)} to 1_u^{(5)}$) in the photodissociation of Cl₂, Br₂, and I₂by using the spin-orbit configuration interaction (SOCI) method and the semiclassical time-dependent coupled Schrodinger equations. From the configuration analyses of the SOCI wavefunctions, we found that the nonadiabatic transition between $1_u^{(2)}$ and $1_u^{(1)}$ is a noncrossing type, while that between $1_u^{(3)}$ and $1_u^{(4)}$ is a crossing type for all the molecules. The behavior of the radial derivative coupling element between $1_u^{(1)}$ and $1_u^{(2)}$ and that between $1_u^{(3)}$ and $1_u^{(4)}$ is analyzed in detail. In Cl₂, nonadiabatic transitions can take place even between the states correlating to different dissociation limits, while in Br₂ and I₂, with the usual photon energies e.g. less than 20 eV, nonadiabatic transitions occur only between the states correlating to the same dissociation limits, reflecting the different magnitudes of the spin-orbit interactions.

• ETRI Journal
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• v.17 no.3
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• pp.17-43
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• 1995

We present a comprehensive derivation of the transport of holes involving an interacting two-valence-band system in terms of a generalized relaxation time approach. We sole a pair of semiclassical Boltzmann equations in a general way first, and then employ the conventional relaxation time concept to simplify the results. For polar optical phonon scattering, we develop a simple method th compensate for the inherent deficiencies in the relaxation time concept and apply it to calculate effective relaxation times separately for each band. Also, formulas for scattering rates and momentum relaxation times for the two-band model are presented for all the major scattering mechanisms for p-type GaAs for simple, practical mobility calculations. Finally, in the newly proposed theoretical frame-work, first-principles calculations for the Hall mobility and Hall factor of p-type GaAs at room temperature are carried out with no adjustable parameters in order to obtain a direct comparison between the theory and recent available experimental results, which would stimulate further analysis toward better understanding of the complex transport properties of the valence band. The calculated Hall mobilities show a general agreement with our experimental data for carbon doped p-GaAs samples in a range of degenerate hole densities. The calculated Hall factors show $r_H$=1.25~1.75 over all hole densities($2{\times}10^{17}{\sim}1{\times}10^{20}cm^{-3}$ considered in the calculations.

• Journal of the Korean Chemical Society
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• v.28 no.1
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• pp.26-33
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• 1984

The rate constants for the following vibration-to-vibration energy exchange reactions have been calculated theoretically for the temperature range from 300 to 800K and for n = 2 to 5. HF(v=n) + DF(v=0) ${\to}$ HF(v=n-l) + DF(v=l) + ${\Delta}E$(a) DF(v=n) + HF(v=0) ${\to}$ DF(v=n-l) + HF(v=l) + ${\Delta}E$(b) In calculation the loosely-held, non-rigid dimer collision model and semiclassical method have been employed. The results show that the rate constants for the processes (a) are much greater than those for the processes (b). Also, it is found that the rate constants for the processes (a) increase with decreasing temperature and with increasing quantum number, while those for the processes (b) show the opposite tendencies. These findings are explained in terms of the sign and magnitude of the energy mismatch, ${\Delta}E$.