Chipman Daniel M
Radiation Laboratory, University of Notre Dame, Notre Dame, IN 46556, USA.
J Chem Phys. 2005 Jan 22;122(4):44111. doi: 10.1063/1.1830438.
The lowest electronic states that are initially formed upon excitation of small water clusters having a central water molecule with one stretched OH bond are studied with electronic structure methods. It is found that in water dimer, trimer, and pentamer the lowest excited singlet and triplet states are each nondissociative for stretching of an OH bond that is hydrogen bonded in an icelike configuration to a neighboring water molecule. This is in marked contrast to the behavior of an isolated gas phase water monomer, where it is well known that the lowest excited state is strongly dissociative upon OH stretching. The conclusions of this study may serve as a basis to interpret recent experimental evidence that suggests a significant lifetime for excited water in irradiated thin ice films, and may also have important implications for the behavior of excitation of liquid water.
利用电子结构方法研究了具有一个中心水分子且其中一个OH键被拉伸的小水团簇激发后最初形成的最低电子态。研究发现，在水二聚体、三聚体和五聚体中，对于以冰状构型与相邻水分子形成氢键的OH键的拉伸，最低激发单重态和三重态均为非解离态。这与孤立气相水单体的行为形成显著对比，在孤立气相水单体中，众所周知，最低激发态在OH键拉伸时会强烈解离。本研究的结论可作为解释近期实验证据的基础，该证据表明辐照薄冰膜中激发态水具有显著的寿命，并且可能对液态水的激发行为也具有重要意义。
