PICOSECOND FLASH-PHOTOLYSIS OF CIS-STILBENE AND TRANS-STILBENE - OBSERVATION OF AN INTENSE INTRA-MOLECULAR CHARGE-RESONANCE TRANSITION

Extremely intense and sharp Sn←S1 absorption of cis- and trans-stilbene was observed with a picosecond flash technique. The decay of the transient absorption of trans-stilbene was exponential with one component (110±10 ps), being same as the fluorescence decay at room temperature, and thus assigned to the Sn←S1 absorption. The molar coefficient of the absorption was 7×105 M-1 cm-1 with the full width at half maximum of 1×103 cm-1. The band width had a strong temperature dependence and became only 500 cm-1 at 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 charge-resonance among the ethylenic and two phenyl moieties in stilbene. © 1979 American Institute of Physics.