Ultrafast pump-probe spectroscopy of electronic excitation transfer in random molecular systems and in photosynthetic antennae

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:7031442

Causgrove, T P

Optical pump-probe (transient absorption) spectroscopy was used to study excitation energy transfer (EET) in random molecular systems and in antenna complexes of photosynthetic organisms. Energy transfer was first studied for Rhodamine 640 adsorbed on ZnO and fused silica surfaces at submonolayer coverage. Ground state recovery on fused silica was coverage-dependent due to excitation trapping by dye aggregates; on ZnO recovery was fast and independent of coverage. This can be explained by energy transfer into semiconductor surface states. Also, EET experiments were performed on solutions of Rhodamine 640 in glycerol using both absorption depolarization and the well-known technique of fluorescence depolarization using time-correlated single photon counting. Data from both techniques match within experimental error theoretical predictions, showing the validity of pump-probe techniques in studying EET. The absorption depolarization of the Q{sub x} electronic transition in BChl a-protein from P. aestuarii was monitored, and the anisotropy was found to decay to a constant, nonzero value due to nonrandom chromophore orientations. The timescale of depolarization was found to be consistent with transfer between delocalized exciton states. Results of experiments on the core antenna complex of photosystem I were remarkably similar, showing that local ordering exists in PS I. This also suggests that EET occurs between groups of chromophores in PS I similar to those in the BChl a-protein.

• Research Organization: Iowa State Univ. of Science and Technology, Ames, IA (USA)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 7031442
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102* -- Chemical & Spectral Procedures
ABSORPTION SPECTROSCOPY
AMINES
ANISOTROPY
BIOLOGICAL MATERIALS
CARBOXYLIC ACIDS
CHALCOGENIDES
DYES
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITATION
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
MATERIALS
MINERALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PROTEINS
REAGENTS
RHODAMINES
SEMICONDUCTOR MATERIALS
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTIVE PROPERTIES
SPECTROSCOPY
SURFACE PROPERTIES
TRANSIENTS
ZINC COMPOUNDS
ZINC OXIDES