Ultrafast charge transfer dynamics in the excited state of DCM measured by a 6-fs UV pulse laser

The photoexcited dynamics of a laser dye, 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), in an acetonitrile solution and dimethyl sulfoxide (DMSO) were studied by pump–probe spectroscopy with 6-fs ultraviolet laser. UV light excites the DCM solved any or DMSO into locally excited (LE) state (via S0→S2 excitation), then LE relaxes to charge transfer state. In previous study, mechanism transition from intramolecular (ICT) was not clear just known proceed faster than 100 fs. Our present work has clarified primary process determining time constant (LE→ICT state) be 50 Spectral analysis transient difference-absorption spectrum shown that stimulated emission peak at 2.9 eV.