翻译成英语：PI 的内部包含有大量的发色团例如苯环和羰基在紫外激光照射下这些发色团会大量吸收光子能量并逐渐转化为不稳定的激发态最终导致分子间的化学键发生断裂。

The PI contains a large number of chromophores internally, such as benzene rings and carbonyl groups. Under ultraviolet laser irradiation, these chromophores absorb a large amount of photon energy and gradually convert into unstable excited states, ultimately leading to the breaking of chemical bonds between molecules.