Vibrational coherence transfer characterized with Fourier-transform 2D IR spectroscopy
ABSTRACT Two-dimensional infrared (2D IR) spectroscopy of the symmetric and asymmetric C[Triple Bond]O stretching vibrations of Rh(CO)(2)acac in hexane has been used to investigate vibrational coherence transfer, dephasing, and population relaxation in a multilevel vibrational system. The transfer of coherence between close-lying vibrational frequencies results in extra relaxation-induced peaks in the 2D IR spectrum, whose amplitude depends on the coherence transfer rate. Coherence transfer arises from the mutual interaction of the bright CO stretches with dark states, which in this case reflects the mutual d-pi(*) back bonding of the Rh center to both the terminal carbonyls and the acetylacenonate ligand. For 2D IR relaxation experiments with variable waiting times, coherent dynamics lead to the modulation of peak amplitudes, while incoherent population relaxation and exchange results in the growth of the relaxation-induced peaks. We have modeled the data by propagating the density matrix with the Redfield equation, incorporating all vibrational relaxation processes during all three experimental time periods and including excitation reorientation effects arising from relaxation. Coherence and population transfer time scales from the symmetric to the asymmetric stretch were found to be 350 fs and 3 ps, respectively. We also discuss a diagrammatic approach to incorporating all vibrational relaxation processes into the nonlinear response function, and show how coherence transfer influences the analysis of structural variables from 2D IR spectroscopy.
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ABSTRACT: Recent two-dimensional (2D) electronic spectroscopic experiments revealed that electronic energy transfer in photosynthetic light harvesting involves long-lived quantum coherence among electronic excitations of pigments. These findings have led to the suggestion that quantum coherence might play a role in achieving the remarkable quantum efficiency of photosynthetic light harvesting. Further, this speculation has led to much effort being devoted to elucidation of the quantum mechanisms of the photosynthetic excitation energy transfer (EET). In this review, we provide an overview of recent experimental and theoretical investigations of photosynthetic electronic energy transfer, specifically addressing underlying mechanisms of the observed long-lived coherence and its potential roles in photosynthetic light harvesting. We close with some thoughts on directions for future developments in this area.Annual Review of Condensed Matter Physics 02/2012; 3:333-361. DOI:10.1146/annurev-conmatphys-020911-125126 · 11.91 Impact Factor
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ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.ChemInform 01/2010; 41(4). DOI:10.1002/chin.201004279
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ABSTRACT: Ultrafast multiple-dimensional vibrational spectroscopy has been extensively applied to studies of molecular structures and dynamics in condensed phases. Along with the developments of new laser sources and new concepts, increasing improvements and applications of this technique have brought the understanding of molecular systems to a new level. In this review, we first briefly introduce the basic concepts, experimental setups and applications of the technique. The most recent progresses in applying vibrational energy transfers to determine intermolecular distances and vibrational couplings to determine three dimensional molecular conformations with our high power multiple-mode multiple-dimensional vibrational spectroscopy are then introduced in more details.10/2012; 31(4-4):469-565. DOI:10.1080/0144235X.2012.733116