2レーザーパルスを用いたスチルベン誘導体の共鳴2光子イオン化

概要

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Radical cations of trans-stilbene and substituted trans-stilbenes (stilbenes and the radical cations denote S and S^<●+>, respectively) were generated from the resonant two-photon ionization (TPI) in acetonitrile with irradiation of one-laser (266- or 355-nm laser) and with simultaneous irradiation of two-color two-lasers (266- and 532-nm or 355- and 532-nm lasers) with the pulse width of 5ns each. The formation yields of S^<●+>, the TPI efficiency, depended on the properties of S in the lowest and higher singlet excited state (S(S_1) and S(S_n)), generated from one-photon excitation with 266- or 355-nm laser and from two-photon excitation with simultaneous irradiation of 266- and 532-nm or 355- and 532-nm lasers, respectively. The TPI efficiency using two-color two-lasers increased compared with that using one-laser. It is confirmed that the TPI proceeds through two-step two-photon excitation with the S_0→S_1→S_n transition. In addition to electronic character of S(S_0) which depends on the substituent of S, oxidation potential, and molar absorption coefficient of the S_0→S_1 absorption as well-known important factors for the TPI efficiency, it is shown that properties of S(S_1) and S(S_n) such as lifetimes, electronic characters of S(S_1) and S(S_n), molar absorption coefficient of the S_1→S_n absorption, ionization rate from S(S_n) are also important.
2006-03-18