The radiant energy induced degradation at 293 K of isolated Dl/D2/cyt b559 complexes from spinách was investigated under aerobic conditions by measurements of absorption and emission spectra between 1.1 and 270 K. In the 1.1 K absorption spectrum a bleaching and slight blue shift at 679 nm and a blue shift of the 672 nm band was observed. In the emission spectrum deconvoluted into Gaussian bands, the major fluorescence band referred to as F682 was most susceptible to photodegradation: (7) At all temperatures F682 was blue shifted with respect to the control. (2) The half-width of F682 was temperature independent at T < 10 K and became significantly increased in damaged samples. (3) The temperature dependence of rp6g2 in the range of 10 K < T < 270 K was less pronounced in damaged samples. Our results support the idea of a multistep model of photodegradation with several intermediates in the pathway from the undamaged control into strongly damaged complexes. The temperature dependence of rp6g2 i® explained by contributions owing to static and dynamical inhomogeneous broadening. The static inhomogeneous broadening increases with progressing degradation. Furthermore, our results suggest that aerobic photodegradation of the Dl/D2/cyt 3559 complexes also causes modifications of the electron-phonon interactions. The frequency of the phonon mode dominating the electron phonon coupling decreases in damaged samples.