Photoelectron Imaging Spectroscopy of the Small Sodium Cluster Anions Na3鈥?/sup>, Na5鈥?/sup>, and Na7鈥?/sup>
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- 作者：Christof Bartels ; Christian Hock ; Raphael Kuhnen ; Bernd v. Issendorff
- 刊名：Journal of Physical Chemistry A
- 出版年：2014
- 出版时间：September 18, 2014
- 年：2014
- 卷：118
- 期：37
- 页码：8270-8276
- 全文大小：317K
- ISSN：1520-5215
文摘
We present a photoelectron imaging study of the small sodium cluster anions Na3鈥?/sup>, Na5鈥?/sup>, and Na7鈥?/sup> at photon energies in the visible and near UV range (hv = 1.64鈥?.28 eV). The resulting angular distributions are remarkably diverse and exhibit a strong dependence on photon energy; only for hv > 3.5 eV do they evolve into more uniform distributions peaked in the direction of the laser polarization. We show that different energy dependencies of the distributions are related to different angular-momentum characters of the bound states. The jellium s-like character of the lowest single-particle states results in photoelectron emission parallel to the laser polarization at all photon energies, whereas the p-like character of the higher states leads to essentially isotropic distributions at threshold and a strong variation with photon energy. Close to the detachment threshold, the asymptotic angular distributions are attributed to the approximate validity of Wigner鈥檚 law, which states that the spectrum is dominated by the partial wave with the smallest angular momentum. For the planar cluster Na5鈥?/sup>, we observe characteristically different behavior for electrons detached from the two in-plane p-like states, and we show how this correlates with the molecular symmetry. Our results indicate that a simple jellium-like description of the molecular orbitals is appropriate for the three-dimensional cluster Na7鈥?/sup>, despite the energetic splitting of the normally triply degenerate 1p level.