Dr. Gerald J. Small
Department of Chemistry
Iowa State University
Iowa

Friday, February 28, 1997
3:00 pm (CT)
3269 Beckman Institute

Abstract

Spectral hole burning spectroscopies are powerful approaches for elucidating the electronic structure and excitation energy transfer/relaxation mechanisms of photosynthetic antenna complexes. Importantly, the hole spectra provide nformation on glass-like structural heterogeneity (inhomogeneous broadening of spectroscopic transitions), electron-vibration and -phonon coupling which is essential input for energy transfer theories. when combined with high pressure (~ 800 MPa) at variable temperature, hole burning becomes even more powerful. In this talk focus will be on the B800fiB850 energy transfer mechanism and exciton level structure of the strongly coupled ring of B850 BChl a molecules. Data for Rps. acidophila, Rb. sphaeroides and Rs. molischianum will be discussed. The data permit determination of the level structure of the B850 absorption band, including the location of the lowest energy and weakly absorbing exciton level of A symmetry (B870). The importance of energy disorder is emphasized. Finally, the mechanism for ~ 100 fs inter-exciton level relaxations of the B850 moleculares is discussed.

Tea and coffee will be served in R3151 Beckman Institute at 2:15pm.