Laser-induced photochemical reaction of bis(ethynylstyryl) benzene prepared by molecular beam deposition.

We have investigated the photochemical reaction in the external photon field induced with KrF excimer laser (λ=248nm) for the bis(ethynylstyryl)benzene (BESB) films deposited by a molecular beam deposition technique. The cis-cis isomer crystalline films have grown on the KBr (001) substrate without laser irradiation. The laser irradiation to the film surface after and during deposition at the substrate temperature of 25°C caused the cis-to-trans photoisomerization and gave amorphous films due to disordering of the molecular arrangement. On the contrary, the photoisomerized trans-trans isomer crystals were found to be grown upon the irradiation during deposition at the substrate temperature of 60°C. These results indicate that the applied photon field to the molecular beam and the substrate temperatures during deposition play a significant role in thefilm structures.