Figure 2.

Fluorescence-excitation spectrum from an individual B800–820/850 LH2 complex from Rps. palustris as a function of the polarization of the excitation light. (A) (Top) Stack of 410 individual spectra recorded consecutively. Between two successive spectra, the polarization of the incident radiation has been rotated by 6.4°. The horizontal axis corresponds to the photon energy, the vertical axis corresponds to the scan number (or equivalently to the polarization angle), and the intensity is coded by the gray scale. The excitation intensity was 50 W cm⁻². (Bottom) Spectrum that corresponds to the average of the 410 consecutively recorded spectra. (B) (Top) Expanded view of the fluorescence intensity of the four bands (B1–B4) marked by the arrows in the lower part as a function of the polarization of the incident radiation (dots) together with cos²-type functions (black) fitted to the data. (Bottom) Two fluorescence-excitation spectra from the stack that correspond to mutually orthogonal polarization of the excitation light.