Figure 1

(a) Top view of the arrangement of the bacteriochlorophyll $a$ molecules in the B800 ring of Rs. molischianum. The protein backbone and all other chromophores have been omitted for clarity. (b) Fluorescence-excitation spectra of the B800 band from LH2 complexes of Rs. molischianum. The top traces show the comparison between an ensemble spectrum (bold line) and the sum of 24 spectra recorded from individual complexes (solid line). The lower three traces display spectra from single LH2 complexes. Each spectrum has been averaged over all possible excitation polarizations. The vertical scale is valid for the lowest trace, all other traces were offset for clarity. All spectra were recorded at 1.4 K with an excitation intensity of $10\mathrm{W}/{\mathrm{c}\mathrm{m}}^2$.Reuse & Permissions

Figure 2

(a) Two-dimensional representation of 513 fluorescence-excitation spectra from a part of the B800 band of an individual LH2 complex recorded consecutively at a scan speed of $3\mathrm{n}\mathrm{m}/\mathrm{s}$ and an excitation intensity of $10\mathrm{W}/{\mathrm{c}\mathrm{m}}^2$. The gray scale gives the fluorescence intensity. Between two successive scans the polarization of the incident radiation has been turned by 1.8°. The horizontal axis corresponds to wave number and the vertical axis to polarization. (b) Average of all 513 spectra. (c) Intensity of the fluorescence for the two absorptions indicated by the boxes in (a) as a function of the polarization of the excitation. The full and dashed lines correspond to ${cos}^2[\alpha (t)+\alpha ]$-type functions fitted to the experimental data with phase angles, $\alpha$, of 148° and 57°, respectively. (d) Histogram of mutual orientations of the transition-dipole moments from 88 absorption lines from 24 individual complexes.Reuse & Permissions

Figure 3

Two-dimensional representation of a part of 614 fluorescence-excitation spectra from an individual B800 ring. Between two successive scans the polarization has been turned by 1.8°. The arrows show the orientation of the transition-dipole moments of the individual absorptions with respect to a laboratory frame. The aquisition times for intervals A, B, and C are 73, 31, and 65 min, respectively. Experimental conditions as in Fig. 2. For more details see text.Reuse & Permissions

Figure 4

Dependence of the orientation of the transition-dipole moments ${\overrightarrow{\mu }}_{+}$ (upper curve) and ${\overrightarrow{\mu }}_{-}$ (lower curve) on the ratio $V/\delta$. The orientations of the initial transition moments ${\overrightarrow{\mu }}_1$ and ${\overrightarrow{\mu }}_2$ were set to 0° and 45° and provide the reference frame.Reuse & Permissions