Hydrogen transfer in excited pyrrole-ammonia clusters
Hydrogen transfer in excited pyrrole-ammonia clusters
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DOI：
10.1063/1.1704639
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发表时间：
2004-06-01
影响因子：
4.4
通讯作者：
Sobolewski, AL
中科院分区：
文献类型：
--
作者：
David, O;Dedonder-Lardeux, C;Sobolewski, AL
本文研究了吡咯-氨簇合物[PyH-（NH_3）（n）+hnu-->Py-.+（NH4）-N-。（NH3）（n-1）]。该反应通过使用延迟电离的双色R2 P1实验清楚地证明，并呈现约235 nm（5.3 eV）的阈值。通过皮秒时间尺度的实验研究了团簇动力学。团簇在10-30 ps范围内衰减，寿命随团簇尺寸增加而增加。反应产物的出现时间与母体团簇的衰变时间相似。蒸发过程中也观察到竞争的反应，蒸发后的集群寿命估计为10 ns左右。反应产物的动能较大，能量分布呈准单动力学分布。这些实验结果排除了反应通过直接N-H键断裂进行的假设，而是暗示存在相当长寿命的中间态。在CASSCF/CASMP 2水平上进行的计算证实了实验观察结果，并提供了一些关于反应机理的提示。(C)2004年，美国物理学会。
The excited state hydrogen atom transfer reaction (ESHT) has been studied in pyrrole-ammonia clusters [PyH-(NH3)(n)+hnu-->Py-.+(NH4)-N-.(NH3)(n-1)]. The reaction is clearly evidenced through two-color R2P1 experiments using delayed ionization and presents a threshold around 235 nm (5.3 eV). The cluster dynamics has also been explored by picosecond time scale experiments. The clusters decay in the 10-30 ps range with lifetimes increasing with the cluster size. The appearance times for the reaction products are similar to the decay times of the parent clusters. Evaporation processes are also observed in competition with the reaction, and the cluster lifetime after evaporation is estimated to be around 10 ns. The kinetic energy of the reaction products is fairly large and the energy distribution seems quasi mono kinetic. These experimental results rule out the hypothesis that the reaction proceeds through a direct N-H bond rupture but rather imply the existence of a fairly long-lived intermediate state. Calculations performed at the CASSCF/CASMP2 level confirm the experimental observations, and provide some hints regarding the reaction mechanism. (C) 2004 American Institute of Physics.