Picosecond flash photolysis ofcishyphen; andtranshyphen;stilbene. Observation of an intense intramolecular chargehyphen;resonance transition

摘要

Extremely intense and sharpSnlarr;S1absorption ofcishyphen; andtranshyphen;stilbene was observed with a picosecond flash technique. The decay of the transient absorption oftranshyphen;stilbene was exponential with one component (110plusmn;10 ps), being same as the fluorescence decay at room temperature, and thus assigned to theSnlarr;S1absorption. The molar coefficient of the absorption was 7times;105Mminus;1cmminus;1with the full width at half maximum of 1times;103cmminus;1. The band width had a strong temperature dependence and became only 500 cmminus;1at 77 K. A theoretical calculation, using a semiempirical Hamiltonian of PPP type, was made to analyze the nature of this observed intense absorption, and was found that the character of the transition was of the chargehyphen;resonance among the ethylenic and two phenyl moieties in stilbene.