Photochemical hole-burning spectroscopy of a photosynthetic reaction center mutant with altered charge separation kinetics: Properties and decay of the initially excited state

Journal Article · Thu Nov 28 04:00:00 EST 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100177a093· OSTI ID:6923522

Middendorf, T R; Mazzola, L T; Boxer, S G ^[1]; Gaul, D F; Schenck, C C ^[2]

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1. Stanford Univ., CA (United States)
2. Colorado State Univ., Fort Collins (United States)

Photochemical hole-burning spectra have been obtained for the lowest energy electronic absorption band of the primary electron donor P of photosynthetic reaction centers (RCs) that exhibit different rates for the initial charge separation step. Wild type (WT) and Tyr(M)210 [yields] Phe mutant [(M)Y210F] RCs from Rhodobacter sphaeroides were studied at 1.5 K in 50% glycerol/buffer glasses. In both types of RC, difference spectra obtained by using narrow-bandwidth excitation on the low-energy edge of the P band display weak, narrow zero-phonon holes coincident with the laser wavelengths, in addition to a broad background bleach of much larger amplitude. The zero-phonon hole width in each type of RC corresponds quantitatively to the broadening expected from the excited-state lifetime. These results are inconsistent with electronic relaxation of the excited state of P prior to electron transfer. The agreement between the time- and frequency-domain experiments may result from vibrational thermalization prior to electron transfer. An alternative mechanism, which does not invoke subpicosecond vibrational thermalization and which is consistent with a wide range of data, is also presented. Quantitative estimates were obtained for the total electron-phonon coupling strength (Huang-Rhys factor) S and for the magnitudes of the homogeneous and inhomogeneous broadening in the P absorption band from self-consistent simulations of the 1.5 K absorption and hole spectra from a linear electron-phonon coupling model. The vibronic and line-width parameters deduced from the simulations are very similar for Wt and (M)Y210F RCs.

• OSTI ID: 6923522
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:24; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505 -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ABSORPTION SPECTROSCOPY
CHEMISTRY
DATA
ENERGY LEVELS
EXCITED STATES
INFORMATION
LIFETIME
MATHEMATICAL MODELS
NUMERICAL DATA
PHONONS
PHOTOCHEMISTRY
PHOTOSYNTHETIC REACTION CENTERS
QUASI PARTICLES
SPECTROSCOPY
THEORETICAL DATA