Crespo-Hernández Carlos E, Arce Rafael
Department of Chemistry, University of Puerto Rico, San Juan 00931-3346, USA.
Photochem Photobiol. 2002 Sep;76(3):259-67. doi: 10.1562/0031-8655(2002)076<0259:podarb>2.0.co;2.
The 266 nm nanosecond laser photolysis of various purine and pyrimidine derivatives results in their photoionization (PI) as one of the primary photochemical pathways. Electron photoejection occurs through a combination of one- and two-photon mechanisms. The PI values depend on the substituents attached to the chromophore of the base. The net PI of the purine bases at 266 nm are of the same order of magnitude (10(-2)) as those of the pyrimidine bases under similar experimental conditions. The monophotonic component is approximately one-third of the net PI yield of the bases. A nonrelaxed singlet excited state intermediate is tentatively proposed for this pathway. It is proposed that this state is significantly stabilized by water solvation, transforming it into a charge transfer to solvent state from which the hydrated electron evolves.
266纳米纳秒激光对各种嘌呤和嘧啶衍生物进行光解，会导致其发生光电离（PI），这是主要的光化学途径之一。电子光发射通过单光子和双光子机制的结合而发生。PI值取决于连接在碱基发色团上的取代基。在相似实验条件下，嘌呤碱基在266纳米处的净PI与嘧啶碱基的净PI处于相同数量级（10(-2)）。单光子成分约为碱基净PI产率的三分之一。对于该途径，初步提出了一种非弛豫单重激发态中间体。据推测，该状态通过水溶剂化得到显著稳定，将其转变为电荷转移至溶剂状态，水合电子由此产生。
