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

将含有荧光分子（如蒽、二苯基蒽、二氰蒽、芘或光致变色分子）的聚合物薄膜（源膜）覆盖整齐的聚合物薄膜（靶膜），并用纳秒脉冲激光从靶膜后方照射。在靶膜表面发现了这些分子的荧光模式，即使激光辐照量小于源膜的烧蚀阈值。通过荧光强度的降低估计出源膜中喷射分子的数量。结果表明，源膜的玻璃化转变温度越低，抛射分子的数量越大。利用全内反射荧光光谱法测定了靶膜表面植入层的厚度。发现分子聚集体的数量随着激光照射次数的增加而增加。从光热温度跳变和热活化扩散的角度探讨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.