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Author Peloquin, J. M. ♦ Lin, S. ♦ Taguchi, A. K. W. ♦ Woodbury, N. W.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword BIOLOGY AND MEDICINE, BASIC STUDIES ♦ CHEMISTRY ♦ PHYSICS ♦ PHOTOCHEMICAL REACTIONS ♦ ABSORPTION SPECTRA ♦ PHOTOSYNTHESIS ♦ PROTEINS ♦ KINETICS ♦ GROUND STATES ♦ EXCITED STATES ♦ HOLES
Abstract Excitation with spectrally narrow (5 nm), temporally short duration(200 fs) laser pulses at a variety of wavelengths between 848 and 903 nmresults in substantial excitation wavelength dependent differences inthe evolution of the bacterial reaction center absorbance spectrum both before and after charge separation occurs. The transient holes in theinitial electron donor band showed a more resolved vibrational bandstructure at 20 K, when compared to those of earlier room temperaturetransient hole-burning experiments. The dominant vibrational bandobserved is at 120 cm{sup -1}, in agreement with dynamic measurementsof coherent oscillations on this time scale. At both room temperatureand low temperature, there is a distribution of P to P{sup *} transitionenergies due to a distribution of the protein conformations in the ground state. At 20 K, one can also see a distribution of P{sup *} to Pstimulated emission energies. As might be expected, the barriers toconformational interconversion are more easily crossed at roomtemperature, resulting in a smaller difference between the meantransition energies of the photoselectable subpopulations on thepicosecond time scale relative to those at low temperature. At 20 K,much of this conformational interconversion is apparently lost whenexciting near the 0-0 transition wavelength of P. 45 refs., 10 figs.
ISSN 00223654
Educational Use Research
Learning Resource Type Article
Publisher Date 1996-08-15
Publisher Place United States
Journal Journal of Physical Chemistry
Volume Number 100
Issue Number 33


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