Events

Quantum Transport Effects and Coherent Ultrafast Multidimensional Spectroscopy of Light Harvesting Photosynthetic Complexes

March 16, 2010 at 3pm/36-428

Shaul Mukamel
Department of Chemistry, University of California, Irvine

abstract:
The harvesting of solar energy and its conversion to chemical energy is essential for all forms of life. Whether quantum effects persist in the energy transport is under active debate. If confirmed, these may explain the high efficiency of light harvesting and open up applications to quantum computing and information processing stemming from entanglement of chromophores. Exciton dynamics simulations in the photosynthetic reaction center of photosystem II based on a novel quantum exciton dissipation theory clearly establish oscillatory energy transport at room temperature originating from interference of quantum pathways. These may be observed through temporal oscillations of time-resolved two dimensional coherent optical spectra. Our simulations reveal that quantum energy transfer effects may persist over the energy transport timescale at room temperature despite the rapid decoherence effects due to environment fluctuations. The response of photosynthetic light harvesting complexes to sequences of femtosecond optical pulses provides multidimensional snapshots of their structure and electronic dynamics. Two-dimensional (2D) signals show characteristic cross-peak patterns which carry information about structures, fluctuations and the entire pathways of energy and charge transfer. The signals reveal couplings between chromophores, and quantum coherence signatures of chromophore entanglement. Coherent quantum pathways and incoherent energy hopping processes may be resolved. Future extensions of multidimensional techniques to the attosecond regime using x-ray pulses will be discussed. Since core excitations are highly localized at selected atoms such signals can monitor the motions of valence electron wavepackets in real space with atomic spatial resolution. Common principles underlying coherent spectroscopy techniques for spins, valence electrons, and core electronic excitations, spanning frequencies from radiowaves to hard X-rays will be discussed.

“Coherent Multidimensional Optical Probes for Electronic Correlations and Exciton Dynamics; from NMR to X-rays”, S. Mukamel, D. Abramavicius, L. Yang, W. Zhuang, I.V. Schweigert and D. Voronine. Acct.Chem.Res. Acct.Chem.Res. 42, 553-562 (2009).
“Coherent Multidimensional Optical Spectroscopy Excitons in Molecular Aggregates; Quasiparticle vs. Supermolecule Perspectives”, D. Abramavicius, B. Palmieri, D. Voronine, F. Sanda and S. Mukamel, Chem. Rev. 109, 2350-2408 (2009).
“Coherent Multidimensional Vibrational Spectroscopy of Biomolecules; Concepts, Simulations and Challenges”. W. Zhuang, T. Hayashi and S. Mukamel, Agnew Chem. Int.Ed. 48, 3750-3781 (2009).

bio:
Shaul Mukamel received his B.Sc degree in Chemical Physics in 1969 and his Ph.D. in 1976 both from Tel Aviv University. He served on the faculty of the Weizmann Institute and Rice University and in 1982 he joined the chemistry department of the University of Rochester and became a professor in 1985. In 2000 he became the Kenneth Mees Professor and in 2003 was appointed joint Professor of Physics. Since 2003 he serves on the faculty of UC Irvine as a Chancellor Professor of Chemistry. Professor Mukamel’s group interests focus on the design of novel ultrafast multidimensional coherent optical spectroscopies for probing and controlling electronic and vibrational molecular dynamics in the condensed phase; Theoretical and computational studies and applications include attosecond nonlinear x-ray spectroscopy of molecules; Many-body theory of optical and photonic materials; a time dependent reduced density matrix framework for computing electronic excitations and nonlinear optical spectroscopy of conjugated polymers, molecular nanostructures, chromophore aggregates and semiconductor and solar cell nanoparticles; Folding and dynamical fluctuations in proteins and DNA; Long range electron transfer, energy funneling, and collective nonlinear optical response of biological light harvesting complexes; Photon statistics in single molecule spectroscopy; Nonlinear dynamics and fluctuations in quantum and classical optical response. Mukamel is a Fellow of the American Physical Society and the Optical Society of America. He is the recipient of the Alfred P. Sloan, the Guggenheim, the Alexander von Humboldt Senior Scientist Award and the 2003 Lippincott award of the OSA.