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Abstract:
Polarization spectroscopy of photochemically produced spectral holes has been used to obtain the line-narrowed spectrum of the first electronic transition of meso-tetraphenylporphin (TPP) in a PMMA matrix at 10 K. The spectral holes have been burned through irradiation with a pulsed dye laser into the spectral region of several vibronic transitions with overlapping inhomogeneous bands. The corresponding satellite holes were detected in the spectral region of the electronic origin. More than 50 lines have been observed up to vibrational wavenumbers of 1850 cm−1 above the electronic origin. The inhomogeneously broadened absorption spectrum displays only two broad bands in this spectral region. The vibrational frequencies of the first excited electronic state of TPP obtained in this way agree very well with those obtained for the same molecule with fluorescence spectroscopy in a supersonic jet, in a polystyrene matrix, and a crystalline Shpol'skii host. They are also very similar to those of the electronic ground state known from resonance Raman spectra. An analysis of the linewidths of resonant holes and satellite holes reveals a small effect of the inhomogeneous site distribution on the vibrational frequencies.
