Study on the Propagation and Localization of Laser-Superheated Molecules in Organic Solids

用整齐的聚合物膜(靶膜)覆盖含荧光分子的聚合物膜(靶膜)，并从靶膜的背面用纳秒脉冲激光照射。当激光能量密度小于源薄膜的烧蚀阈值时，目标薄膜表面仍存在这些分子的荧光图案。通过荧光强度的降低来估计从源膜射出的分子的量。研究发现，源膜的玻璃化转变温度越低，喷射量越大。用全内反射荧光光谱仪测定了靶膜表面注入的膜层厚度。分子聚集体的数量随着激光击发次数的增加而增加。结合聚合物固体中的光热温度跃迁和热激活扩散，讨论了重复辐照对荧光分子的穿透和聚集机理。

Polymer films involving fluorescent molecules such as anthracene, diphenyl anthracene, dicyano anthracene, pyrene, or photochromic melecules (source films) were overlaid with neat polymer films (target films), and irradiated with nanosecond pulsed laser from the rear of the target films. Fluorescent patterns of these molecules were found at the surface of the target films even when the laser fluence was less than the ablation threshold of the source films. The amount of ejected molecules from the source film was estimated from the reduction of fluorescence intensity. It was found that the lower the glass transition temperature of the source film, the higher the amount of ejected molecules. The thickness of the implanted layr at the surface of the target film was obtained by means of total internal reflection fluorescence spectroscopy. The amount of molecular aggregates was found to increase with increasing the number of laser shots. The mechanism of the penetration and aggregation of the fluorescent molecules by repetitive irradiation was discussed in connection with photothermal temperature jump and thermally activated diffusion in polymer solids.