LOW-TEMPERATURE OPTICAL SPECTROSCOPY OF NATURAL PORPHYRINS

Low temperature hole burning excitation fluorescence spectra of a set of uroporphyrin I esters in. amorphous (chloroform) matrix are presented. The hole burning spectra were excited within the region of the 0-0 S1 --> S0 transition and measured in the temperature range 1.5 - 4.3 K. From the fluence the values of homogeneous linewidths were determined. The temperature dependence of the holewidth delta(HB) has been studied. The temperature dependence of delta(HB) follows the power law T(alpha) and coefficients alpha for uroporphyrin I esters are within the range 1.32 - 1.36, which is in good agreement with other results obtained for systems in amorphous matrices. The fluorescence lifetime values of GAMMA(hom) and zero-temperature extrapolated values are compared.