Excited states of the water molecule:: Analysis of the valence and Rydberg character
Excited states of the water molecule:: Analysis of the valence and Rydberg character
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DOI：
10.1063/1.2837827
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发表时间：
2008-03-14
影响因子：
4.4
通讯作者：
Merchan, Manuela
中科院分区：
文献类型：
--
作者：
Rubio, Mercedes;Serrano-Andres, Luis;Merchan, Manuela
用扩展的量子化学多态CASPT 2方法，即MS-CASPT 2，结合原子自然轨道型的单电子基组，对水分子的激发态进行了分析.该研究包括13个单重态和三重态激发态，价态和3s-，3 p-和3d-里德伯系列成员收敛到最低电离势，3s-和3 p-Rydberg成员收敛到阳离子的第二个低位态，1（2）A（1）。这些研究主要集中在低激发态的价态或里德堡性质的分析上。对不同几何构型的水的1 B-1（1）态的计算表明，在分子的平衡几何构型下，它具有主要的3s-Rydberg特征，但在O-H键伸长时，它逐渐变成主要由单电子1 B（1）-> 4a（1）促进描述的价态，正如普通化学教科书所预期的那样。所描述的价-里德伯混合是由分子轨道里德伯化过程产生的，正如R. S. Mulliken [Acc.Chem.Res.9，7（1976）]。同样的现象也发生在1（1）A（2）状态，而一个更复杂的行为已被确定为2（1）A（1）状态，其中MO里德伯化和构型混合发生。对于分子的三重态也得到了类似的结论。(c)2008年美国物理学会。
The excited states of the water molecule have been analyzed by using the extended quantum-chemical multistate CASPT2 method, namely, MS-CASPT2, in conjunction with large one-electron basis sets of atomic natural orbital type. The study includes 13 singlet and triplet excited states, both valence and 3s-, 3p-, and 3d-members of the Rydberg series converging to the lowest ionization potential and the 3s- and 3p-Rydberg members converging to the second low-lying state of the cation, 1 (2)A(1). The research has been focused on the analysis of the valence or Rydberg character of the low-lying states. The computation of the 1 B-1(1) state of water at different geometries indicates that it has a predominant 3s-Rydberg character at the equilibrium geometry of the molecule but it becomes progressively a valence state described mainly by the one-electron 1b(1)-> 4a(1) promotion, as expected from a textbook of general chemistry, upon elongation of the O-H bonds. The described valence-Rydberg mixing is established to be originated by a molecular orbital (MO) Rydbergization process, as suggested earlier by R. S. Mulliken [Acc. Chem. Res. 9, 7 (1976)]. The same phenomenon occurs also for the 1 (1)A(2) state whereas a more complex behavior has been determined for the 2 (1)A(1) state, where both MO Rydbergization and configurational mixing take place. Similar conclusions have been obtained for the triplet states of the molecule. (c) 2008 American Institute of Physics.