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- John S. Briggs, Alexander Eisfeld
- Physical review. E, Statistical, nonlinear, and…
- 2011

To investigate the effect of quantum coherence on electronic energy transfer, which is the subject of current interest in photosynthesis, we solve the problem of transport for the simplest model of an aggregate of monomers interacting through dipole-dipole forces using both quantum and classical dynamics. We conclude that for realistic coupling strengths… (More)

- Alexander Eisfeld, John S. Briggs
- Physical review. E, Statistical, nonlinear, and…
- 2012

In a previous paper [Phys. Rev. E 83, 051911 (2011)] we have shown that the results of a quantum-mechanical calculation of electronic energy transfer (EET) over aggregates of coupled monomers can be described also by a model of interacting classical electric dipoles in a weak-coupling approximation, which we referred to as the realistic coupling… (More)

for some quantum system S it is usually pointed out that time is a parameter, not enjoying the status of a quantum operator. However, it is almost never pointed out that the time occurring in HS(t) always is a classical time arising from the classical time development (according to Newton or Maxwell equations) of external fields or material particles… (More)

- Alexander Eisfeld, Rolf Kniprath, John S. Briggs
- The Journal of chemical physics
- 2007

A theory of the electronic circular dichroism (CD) and optical rotatory dispersion (ORD) of infinite aggregates exhibiting cylindrical symmetry is presented in which, to the authors' knowledge, for the first time vibrational structure is included explicitly. It is shown that, with the coherent exciton scattering approximation in the Green function approach,… (More)

- Alexander Eisfeld, Lukas B. Braun, Walter T. Strunz, John S. Briggs, J. Warren Beck, Volker Engel
- The Journal of chemical physics
- 2005

We consider three distinct methods of calculating the vibronic levels and absorption spectra of molecular dimers coupled by dipole-dipole interactions. The first method is direct diagonalization of the vibronic Hamiltonian in a basis of monomer eigenstates. The second method is to use creation and annihilation operators leading in harmonic approximation to… (More)

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- Jan J J Roden, Georg Schulz, Alexander Eisfeld, John S. Briggs
- The Journal of chemical physics
- 2009

We examine the transfer of electronic excitation (an exciton) along a chain of electronically coupled monomers possessing internal vibronic structure and which also interact with degrees of freedom of the surrounding environment. Using a combination of analytical and numerical methods, we calculate the time evolution operator or time-dependent Green's… (More)

- J. H. Macek, James B Sternberg, Serge Ovchinnikov, John S. Briggs
- Physical review letters
- 2010

Deep minima in He(e,2e)He+ triply differential cross sections are traced to vortices in atomic wave functions. Such vortices have been predicted earlier, but the present calculations show that they have also been observed experimentally, although not recognized as vortices. Their observation in (e,2e) measurements shows that vortices play an important role… (More)

- D. Dimitrovski, E. A. Solov'ev, John S. Briggs
- Physical review letters
- 2004

We investigate ionization and excitation of H(1s) in the limit of very short electric field pulses, analytically and numerically and both in the limit of small and extremely large peak electric fields. We identify a process of recombination akin to Rabi flopping from the continuum and give an analytic expression for this process after a single-cycle… (More)

- Alexander Eisfeld, John S. Briggs
- Physical review letters
- 2006

We present a simple formula by which the shape of the absorption spectrum of an aggregate of quantum "monomers" (cold atoms, molecules, quantum dots, nanoparticles, etc.) interacting via dipole-dipole forces can be calculated from the averaged spectrum of the quantum monomer itself. Spectral broadening, due to a wide variety of causes, is included… (More)