Photoelectron imaging and theoretical investigation of bimetallic Bi1–2Ga0–2− and Pb1–4− cluster anions

Sobhy, M. A.; Reveles, J. Ulises; Gupta, Ujjwal; Khanna, Shiv N.; Castleman, A. W.

doi:doi:10.1063/1.3069295

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A new method for determining absorption cross sections out of initially excited vibrational states

A first experimental demonstration, combining the methods of vibrationally mediated photodissociation (VMP) and ionization-loss stimulated Raman spectroscopy (ILSRS) for measuring cross sections for dissociation of vibrationally excited levels is reported. The action spectrum obtained in the VMP of methylamine exhibits enhancement of the H photofragment yield as a result of initial vibrational excitation and the ILSRS monitors the fraction of molecules being excited. The partial cross sections ...

Quasiclassical trajectory calculations analyzing the role of vibrational and translational energy in the F+CH₂D₂ reaction

An exhaustive state-to-state dynamics study was performed to analyze the effects of vibrational excitation and translational energy on the dynamics of the F+CH2D2 gas-phase reaction, which are connected to such issues as bond selectivity, mode selectivity, and Polanyi’s rules. This reaction can evolve along two channels: D-abstraction, DF(v′)+CH2D(v′), and H-abstraction, HF(v′)+CHD2(v′). Quasiclassical trajectory calculations were performed on an analytical potential energy surface previously d...

We present the results of photoelectron velocity-map imaging experiments for the photodetachment of small negatively charged Bi_mGa_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_mGa_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 BiGa2− cluster is found to be stable, both because of its even electron number and the high electron affinity of BiGa₂. The measured photoelectron angular distributions of the Bi_mGa_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 BiGa2−, Bi₂Ga3− and Bi₂Ga5− (anionic), and BiGa₃, BiGa₅, Bi₂Ga₄ and Bi₂Ga₆ (neutral) clusters are unusually stable. The stability of the anionic and neutral Bi₂Ga_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 BiGa₃ cluster is rationalized as being similar to BiAl₃, an all-metal aromatic cluster.

Article Outline

INTRODUCTION
EXPERIMENTAL AND COMPUTATIONAL METHODS
RESULTS AND DISCUSSION
CONCLUSIONS

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KEYWORDS and PACS

Keywords

bismuth alloys, density functional theory, electron affinity, electron correlations, electron detachment, electronic structure, gallium alloys, gradient methods, lead, metal clusters, photoelectron spectra

PACS

79.60.Bm

Clean metal, semiconductor, and insulator surfaces
61.46.Bc

Structure of clusters (e.g., metcars; not fragments of crystals; free or loosely aggregated or loosely attached to a substrate)
71.45.Gm

Exchange, correlation, dielectric and magnetic response functions, plasmons
71.15.Mb

Density functional theory, local density approximation, gradient and other corrections
71.20.Gj

Other metals and alloys

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http://dx.doi.org/10.1063/1.3069295

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0021-9606 (print)

1089-7690 (online)

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American Institute of Physics

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