Triplet-singlet difference spectra of Rps. viridis recorded with magneto-optical difference spectroscopy at 1.2–286 K. Temperature dependence of position and width of the long-wavelength absorption band Original Research Article

The long-wavelength absorption band of Rps. viridis has been monitored by magneto-optical difference spectroscopy at temperatures between 1.5 and 286 K. Clear evidence is obtained for two components whose relative contribution is strongly temperature dependent. Plots of linewidth and peak position of the two components (determined by Gaussian fits) as a function of temperature could be well fitted with the standard theory of vibrational broadening, yielding a Huang-Rhys factor S = 4–5 and average mode frequencies of about 70 cm−1. Unlike the values obtained treating the long-wavelength band as a single component, the present parameter values compare well with those derived from holeburning spectroscopy.