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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Lifetimes of Be-3(2-) and Mg-3(2-) Cluster Dianions
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Lifetimes of Be-3(2-) and Mg-3(2-) Cluster Dianions

机译：BE-3（2-）和MG-3（2-）群偶联的寿命

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摘要

The alkaline earth metal trimer cluster dianions Be-3(2-) and Mg-3(2-) lie energetically above their respective monoanions and can therefore decay by electron autodetachment. Consequently, these dianions possess only short-lived resonance states, and here we study these states using regularized analytic continuation as well as complex absorbing potentials combined with a wide a variety of quantum chemistry methods including CCSD(T), SACCI, EOM-CCSD, CASPT2, and NEVPT2. For both Be-3(2-) and Mg-3(2-), four low-energy resonance states corresponding to different occupation patterns of the two excess electrons in the two lowest p-sigma and p-pi orbitals are identified: Two states are dominated by doubly occupied configurations and can be characterized as showing sigma and pi aromatic character. The other two states correspond to the open-shell singlet/triplet pair. All dianion states are found to be highly unstable and to possess short lifetimes: They show resonance positions in the energy range 2.3-4.3 eV above the ground states of their respective monoanions and broad widths between 1 and 1.5 eV translating into femtosecond lifetimes. For both Be-3(2-) and Mg-3(2-), the differences between the four states are small, but the triplet states tend to be slightly more stable than the three singlet states. Thus, in the case of the multicharged ion aromatic character of the excess electrons takes second stage while Coulomb repulsion takes front and center. In addition to the two isolated cluster dianions, model stabilization by small water clusters is explored. Our results show a dramatic drop in resonance position and width corresponding to a lifetime increase by 2 orders of magnitude. However, the "solvated" clusters are still resonances, and a more pronounced perturbation by, for example, yet larger water clusters or a ligand environment providing larger bond dipoles will be needed to fully stabilize two excess electrons localized on a small system such as an alkaline met
机译：碱土金属三聚体团簇二元离子Be-3（2-）和Mg-3（2-）位于其各自的单阴离子上方，因此可以通过电子自动分离进行衰变。因此，这些二价离子只具有短寿命的共振态，在这里，我们使用正则化的解析延拓和复合吸收势，结合各种量子化学方法，包括CCSD（T）、SACCI、EOM-CCSD、CASPT2和NEVPT2，研究这些态。对于Be-3（2-）和Mg-3（2-），在两个最低的p-sigma和p-pi轨道中，识别出四个低能共振态，对应于两个过剩电子的不同占据模式：两个态以双占据构型为主，并且可以表征为显示sigma和pi芳香特性。另外两种状态对应于开壳单重态/三重态对。研究发现，所有二元离子态都高度不稳定，寿命较短：它们的共振位置位于各自单阴离子基态上方2.3-4.3 eV的能量范围内，宽度在1到1.5 eV之间，转换为飞秒寿命。对于Be-3（2-）和Mg-3（2-），四个态之间的差异很小，但三重态往往比三个单重态略稳定。因此，在多电荷离子的情况下，过量电子的芳香特性处于第二阶段，而库仑斥力处于前面和中心。除了两个孤立的团簇二离子外，还探讨了小水团簇对模型的稳定作用。我们的结果显示，共振位置和宽度急剧下降，相应的寿命增加了2个数量级。然而，“溶剂化”的团簇仍然是共振，需要更明显的扰动，例如，更大的水团簇或提供更大键偶极子的配体环境，以完全稳定两个位于小系统（如碱性met）上的多余电子

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