Ultrafast conformation equilibration in triphenyl methane dyes analyzed by time resolved induced photoabsorption

Abstract

Dual frequency pump–probe induced photoabsorption recovery is studied in two triphenylmethane dyes, malachite green and crystal violet, using femtosecond laser pulses. Comparison of the decays observed for different polarization conditions allows us to analyze the symmetry of electronic states. We observe that the simplest C2 or D3 symmetries cannot account for all our observations. In addition to the previously reported electronic relaxation decays, we observe two additional subpicosecond relaxation components. A first rising component is attributed to the conformational relaxation of torsional modes and a faster decay can be interpreted as originating from solvent limited vibrational relaxation. We attribute the solvent dependence of these relaxations to the nonrigid nature of the triphenylmethanes.