Photoisomerization processes in the IR-140 laser dye

The photoisomerization processes in the well known IR-140 laser dye and in the closest relevant DTTC model have been investigated by a mode-locked laser spectroscopy in order to observe the influence of a partial rigidization of the polymethine chain. The kinetic, spectral and thermodynamic parameters have been measured; the correlations between the transient quantum yields and the laser efficiency under flash-lamped pumping are discussed. Evidence is given for a surprising solvent effect upon the photoisomerization process.