Photoelectron imaging and theoretical investigation of bimetallic Bi(1-2)Ga(0-2)(-) and Pb(1-4)(-) cluster anions.
Photoelectron imaging and theoretical investigation of bimetallic Bi(1-2)Ga(0-2)(-) and Pb(1-4)(-) cluster anions.
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双金属Bi(1-2)Ga(0-2)(-)和Pb(1-4)(-)簇阴离子的光电子成像和理论研究。
DOI：
10.1063/1.3069295
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
A. Castleman
中科院分区：
文献类型：
--
作者：
M. A. Sobhy;J. Reveles;U. Gupta;S. Khanna;A. Castleman
我们展示了 527 nm 处带负电荷的 Bi(m)Ga(n) (m=1-2, n=0-2) 和 Pb(n) (n=1-4) 团簇光脱离的光电子速度图成像实验结果。光电子图像揭示了这些团簇光电子光谱中的新特征及其角分布。我们报告了从光电子图像中导出的 Bi(m)Ga(n) 和 Pb(n) 团簇所观察到的多个电子带的垂直脱离能及其各自的各向异性参数。 BiGa(n)团簇的实验表明，电子亲和力随着Ga原子数量从n=0到2而增加。BiGa(2)(-)团簇被发现是稳定的，这既是因为其偶数电子数，又是因为BiGa(2)的高电子亲和力。 Bi(m)Ga(n) 和 Pb(n) 团簇的测量光电子角分布取决于轨道对称性和电子动能。对这些簇进行了采用交换相关势的广义梯度近似的密度泛函理论计算，以确定它们的原子和电子结构。通过理论计算，我们发现BiGa(2)(-)、Bi(2)Ga(3)(-)和Bi(2)Ga(5)(-)（阴离子），以及BiGa(3)、BiGa(5)、Bi(2)Ga(4)和Bi(2)Ga(6)（中性）团簇异常稳定。阴离子和中性Bi(2)Ga(n)团簇的稳定性归因于奇偶效应，与奇数电子系统相比，具有偶数电子的团簇通过在先前尺寸中添加Ga原子而呈现出更大的能量增益。中性BiGa(3)簇的稳定性被合理化为与全金属芳族簇BiAl(3)相似。
We present the results of photoelectron velocity-map imaging experiments for the photodetachment of small negatively charged Bi(m)Ga(n) (m=1-2, n=0-2), and Pb(n) (n=1-4) clusters at 527 nm. The photoelectron images reveal new features along with their angular distributions in the photoelectron spectra of these clusters. We report the vertical detachment energies of the observed multiple electronic bands and their respective anisotropy parameters for the Bi(m)Ga(n) and Pb(n) clusters derived from the photoelectron images. Experiments on the BiGa(n) clusters reveal that the electron affinity increases with the number of Ga atoms from n=0 to 2. The BiGa(2)(-) cluster is found to be stable, both because of its even electron number and the high electron affinity of BiGa(2). The measured photoelectron angular distributions of the Bi(m)Ga(n) and Pb(n) clusters are dependent on both the orbital symmetry and electron kinetic energies. Density-functional theory calculations employing the generalized gradient approximation for the exchange-correlation potential were performed on these clusters to determine their atomic and electronic structures. From the theoretical calculations, we find that the BiGa(2)(-), Bi(2)Ga(3)(-) and Bi(2)Ga(5)(-) (anionic), and BiGa(3), BiGa(5), Bi(2)Ga(4) and Bi(2)Ga(6) (neutral) clusters are unusually stable. The stability of the anionic and neutral Bi(2)Ga(n) clusters is attributed to an even-odd effect, with clusters having an even number of electrons presenting a larger gain in energy through the addition of a Ga atom to the preceding size compared to odd electron systems. The stability of the neutral BiGa(3) cluster is rationalized as being similar to BiAl(3), an all-metal aromatic cluster.