TRIPLET-SINGLET DIFFERENCE SPECTRA OF RHODOPSEUDOMONAS-VIRIDIS RECORDED WITH MAGNETOOPTICAL DIFFERENCE SPECTROSCOPY AT 1.2-286 K - TEMPERATURE-DEPENDENCE OF POSITION AND WIDTH OF THE LONG-WAVELENGTH ABSORPTION-BAND

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 relat ive 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 t heory of vibrational broadening, yielding a Huang-Rhys factor S = 4-5 and average mode frequencies of about 70 cm(-1). Unlike the values obt ained treating the long-wavelength band as a single component, the pre sent parameter values compare well with those derived from holeburning spectroscopy.