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Using size-selected anion photoelectron spectroscopy and density functional theory, we investigated the structures and properties of fluorinated bimetallic clusters CoAuF1-2− and CuAuF1-2− and their neutrals. Both experimental and theoretical results show that in these cluster anions, Au behaves like a halogen atom. For example, the measured vertical detachment energies (VDEs) of CoAuF− (2.00 ± 0.08 eV) and CuAuF− (3.8 ± 0.1 eV) are close to those of CoF2− (2.12 ± 0.08 eV) and CuF2− (3.58 ± 0.08 eV), respectively. The theoretical results show that the geometries and electronic structures of CoAuF− and CuAuF− are similar to those of CoF2− and CuF2−. The natural population analysis and natural electron configuration analyses further confirm that the electronic properties of Au in MAuF− (M = Co, Cu) mimic those of MF2−. In addition, the electron localization function analyses show that the M-Au chemical bonds are similar to the corresponding M-F chemical bonds, providing evidence for the ionic nature of the interactions. When a second F atom is attached to the CoAuF− and CuAuF− clusters, the VDEs of the resulting CoAuF2− and CuAuF2− are 4.38 ± 0.08 eV and 3.71 ± 0.08 eV, respectively, indicating their superhalogen character as these values are higher than those of halogen anions. The results may be useful for understanding the properties of gold at the nanoscale that play an important role in catalysis and nanotechnology. [ABSTRACT FROM AUTHOR]

The structures of magnesium chloride dimer-water clusters, (MgCl2)2(H2O)n−/0, were investigated with size-selected anion photoelectron spectroscopy and theoretical calculations to understand the dissolution of magnesium chloride in water. The most stable structures were confirmed by comparing vertical detachment energies (VDEs) with the experimental measurements. A dramatic drop of VDE at n = 3 has been observed in the experiment, which is in accordance with the structural change of (MgCl2)2(H2O)n−. Compared to the neutral clusters, the excess electron induces two significant phenomena in (MgCl2)2(H2O)n−. First, the planar D2h geometry can be converted into a C3v structure at n = 0, making the Mg–Cl bonds easier to be broken by water molecules. More importantly, a negative charge-transfer-to-solvent process occurs after adding three water molecules (i.e., at n = 3), which leads to an obvious deviation in the evolution of the clusters. Such electron transfer behavior was noticed at n = 1 in monomer MgCl2(H2O)n−, indicating that the dimerization between two MgCl2 molecules can make the cluster more capable of binding electron. In neutral (MgCl2)2(H2O)n, this dimerization provides more sites for the added water molecules, which can stabilize the entire cluster and maintain its initial structure. Specifically, filling the coordination number to be 6 for Mg atoms can be seen as a link between structural preferences in the dissolution of the monomers, dimers, and extended bulk-state of MgCl2. This work represents an important step forward into fully understanding the solvation of MgCl2 crystals and other multivalent salt oligomers. [ABSTRACT FROM AUTHOR]

Chromium-doped silicon clusters, CrSin-(n = 3-12), were investigated with anion photoelectron spectroscopy and density functional theory calculations. The combination of experimental measurement and theoretical calculations reveals that the onset of endohedral structure in CrSin- clusters occurs at n = 10 and the magnetic properties of the CrSin- clusters are correlated to their geometric structures. The most stable isomers of CrSin- from n = 3 to 9 have exohedral structures with magnetic moments of 3-5μB while those of CrSi10-, CrSi11-, and CrSi12- have endohedral structures and magnetic moments of 1μB. [ABSTRACT FROM AUTHOR]

Negative ion photoelectron spectra of ZrO-, HfO-, HfHO-, and HfO2H- are reported. Even though zirconium- and hafnium-containing molecules typically exhibit similar chemistries, the negative ion photoelectron spectral profiles of ZrO- and HfO- are dramatically different from one another. By comparing these data with relevant theoretical and experimental studies, as well as by using insights drawn from atomic spectra, spin-orbit interactions, and relativistic effects, the photodetachment transitions in the spectra of ZrO- and HfO- were assigned. As a result, the electron affinities of ZrO and HfO were determined to be 1.26 ± 0.05 eV and 0.60 ± 0.05 eV, respectively. The anion photoelectron spectra of HfHO- and HfO2H- are similar to one another and their structural connectivities are likely to be H-Hf-O- and O-Hf-OH-, respectively. The electron affinities of HfHO and HfO2H are 1.70 ± 0.05 eV and 1.73 ± 0.05 eV, respectively. [ABSTRACT FROM AUTHOR]

We conducted a combined anion photoelectron spectroscopy and density functional theory study on the structural evolution of copper-doped silicon clusters, CuSin- (n = 4-18). Based on the comparison between the experiments and theoretical calculations, CuSi12- is suggested to be the smallest fully endohedral cluster. The low-lying isomers of CuSin- with n ≥ 12 are dominated by endohedral structures, those of CuSin- with n < 12 are dominated by exohedral structures. The most stable structure of CuSi12- is a double-chair endohedral structure with the copper atom sandwiched between two chair-style Si6 rings or, in another word, encapsulated in a distorted Si12 hexagonal prism cage. CuSi14- has an interesting C3h symmetry structure, in which the Si14 cage is composed by three four-membered rings and six five-membered rings. [ABSTRACT FROM AUTHOR]

The nucleobase-gold complexes were studied with anion photoelectron spectroscopy and density functional calculations. The vertical detachment energies of uracil-Au-, thymine-Au-, cytosine-Au-, adenine-Au-, and guanine-Au- were estimated to be 3.37 ± 0.08 eV, 3.40 ± 0.08 eV, 3.23 ± 0.08 eV, 3.28 ± 0.08 eV, and 3.43 ± 0.08 eV, respectively, based on their photoelectron spectra. The combination of photoelectron spectroscopy experiments and density functional calculations reveals the presence of two or more isomers for these nucleobase-gold complexes. The major isomers detected in the experiments probably are formed by Au anion with the canonical tautomers of the nucleobases. The gold anion essentially interacts with the nucleobases through N-H···Au hydrogen bonds. [ABSTRACT FROM AUTHOR]

The entrance channel potentials of the prototypical polyatomic reaction family X + CH4 → HX + CH3 (X = F, Cl, Br, I) are investigated using anion photoelectron spectroscopy and high-level ab initio electronic structure computations. The pre-reactive van der Waals (vdW) wells of these reactions are probed for X = Cl, Br, I by photodetachment spectra of the corresponding X--CH4 anion complex. For F-CH4, a spin-orbit splitting (∼1310 cm-1) much larger than that of the F atom (404 cm-1) was observed, in good agreement with theory. This showed that in the case of the F-CH4 system the vertical transition from the anion ground state to the neutral potentials accesses a region between the vdW valley and transition state of the early-barrier F + CH4 reaction. The doublet splittings observed in the other halogen complexes are close to the isolated atomic spin-orbit splittings, also in agreement with theory. [ABSTRACT FROM AUTHOR]

The electronic structures of CuBO2-, Cu(BO2)2-, Cu2(BO2)-, and Cu2(BO2)2- clusters were investigated using photoelectron spectroscopy. The measured vertical and adiabatic detachment energies of these clusters revealed unusual properties of Cu(BO2)2 cluster. With an electron affinity of 5.07 eV which is larger than that of its BO2 superhalogen (4.46 eV) building-block, Cu(BO2)2 can be classified as a hyperhalogen. Density functional theory based calculations were carried out to identify the ground state geometries and study the electronic structures of these clusters. Cu(BO2) and Cu(BO2)2 clusters were found to form chainlike structures in both neutral and anionic forms. Cu2(BO2) and Cu2(BO2)2 clusters, on the other hand, preferred a chainlike structure in the anionic form but a closed ringlike structure in the neutral form. Equally important, substantial differences between adiabatic detachment energies and electron affinities were found, demonstrating that correct interpretation of the experimental photoelectron spectroscopy data requires theoretical support not only in determining the ground state geometry of neutral and anionic clusters, but also in identifying their low lying isomers. [ABSTRACT FROM AUTHOR]

Small titanium-aluminum oxide clusters, TiAlOy- (y=1-3) and TiAl2Oy- (y=2-3), were studied by using anion photoelectron spectroscopy. The adiabatic detachment energies of TiAlOy- (y=1-3) were estimated to be 1.11±0.05, 1.70±0.08, and 2.47±0.08 eV based on their photoelectron spectra; those of TiAl2O2- and TiAl2O3- were estimated to be 1.17±0.08 and 2.2±0.1 eV, respectively. The structures of these clusters were determined by comparison of density functional calculations with the experimental results. The structure of TiAlO- is nearly linear with the O atom in the middle. That of TiAlO2- is a kite-shaped structure. TiAlO3- has a kite-shaped TiAlO2 unit with the third O atom attaching to the Ti atom. TiAl2O2- has two nearly degenerate Al-O-Ti-O-Al chain structures that can be considered as cis and trans forms. TiAl2O3- has two low-lying isomers, kite structure and book structure. The structures of these clusters indicate that the Ti atom tends to bind to more O atoms. [ABSTRACT FROM AUTHOR]

The equilibrium structure, stability, and electronic properties of the Al13X (X=H,Au,Li,Na,K,Rb,Cs) clusters have been studied using a combination of photoelectron spectroscopy experiment and density functional theory. All these clusters constitute 40 electron systems with 39 electrons contributed by the 13 Al atoms and 1 electron contributed by each of the X (X=H,Au,Li,Na,K,Rb,Cs) atom. A systematic study allows us to investigate whether all electrons contributed by the X atoms are alike and whether the structure, stability, and properties of all the magic clusters are similar. Furthermore, quantitative agreement between the calculated and the measured electron affinities and vertical detachment energies enable us to identify the ground state geometries of these clusters both in neutral and anionic configurations. [ABSTRACT FROM AUTHOR]

The photoelectron spectra of chromium-doped silicon cluster anions, CrSin-, were measured over the size range, n=8–12. Their vertical detachment energies were measured to be 2.71, 2.88, 2.87, 2.95, and 3.18 eV, respectively. Our results support theoretical calculations by Khanna, Rao, and Jena [Phys. Rev. Lett. 89, 016803 (2002)] which found CrSi12 to be an enhanced stability (magic) cluster with its chromium atom encapsulated inside a silicon cage and with its magnetic moment completely quenched by the effects of the surrounding cage. [ABSTRACT FROM AUTHOR]

(Nickel)n(benzene)m- cluster anions were studied by both mass spectrometry and anion photoelectron spectroscopy. Only Nin(Bz)m- species for which n>=m were observed in the mass spectra. No single-nickel Ni1(Bz)m- species were seen. Adiabatic electron affinities, vertical detachment energies, and second transition energies were determined for (n,m)=(2,1), (2,2), (3,1), and (3,2). For the most part, calculations on Nin(Bz)m- species by B. K. Rao and P. Jena [J. Chem. Phys. 117, 5234 (2002)] were found to be consistent with our results. The synergy between their calculations and our experiment provided enhanced confidence in the theoretically implied magnetic moments of several nickel-benzene complexes. The magnetic moments of small nickel clusters were seen to be extremely sensitive to immediate molecular environmental effects. © 2005 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Copper-doped aluminum cluster anions, CuAl[sub n][sup -] were generated in a laser vaporization source and examined via mass spectrometry (n=2-30) and anion photoelectron spectroscopy (n=2-15). The mass spectrum of the CuAl[sub n][sup -] series is dominated by CuAl[sub 13][sup -] with other magic numbers also appearing at n=6, 19, and 23. The electron affinity versus cluster size trend shows a peak at n=6 and a dip at n=13. These results are discussed in terms of the reordering of shell model energy levels and the enhanced stability of neutral CuAl[sub 13]. Reordering, which is a consequence of the copper atom residing in the central region of these clusters, provides an anion-oriented electronic rationale for the observed magic numbers. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Using size-selected anion photoelectron spectroscopy and density functional theory, we investigated the structures and properties of fluorinated bimetallic clusters CoAuF1-2- and CuAuF1-2- and their neutrals. Both experimental and theoretical results show that in these cluster anions, Au behaves like a halogen atom. For example, the measured vertical detachment energies (VDEs) of CoAuF- (2.00 ± 0.08 eV) and CuAuF- (3.8 ± 0.1 eV) are close to those of CoF2- (2.12 ± 0.08 eV) and CuF2- (3.58 ± 0.08 eV), respectively. The theoretical results show that the geometries and electronic structures of CoAuF- and CuAuF- are similar to those of CoF2- and CuF2-. The natural population analysis and natural electron configuration analyses further confirm that the electronic properties of Au in MAuF- (M = Co, Cu) mimic those of MF2-. In addition, the electron localization function analyses show that the M-Au chemical bonds are similar to the corresponding M-F chemical bonds, providing evidence for the ionic nature of the interactions. When a second F atom is attached to the CoAuF- and CuAuF- clusters, the VDEs of the resulting CoAuF2- and CuAuF2- are 4.38 ± 0.08 eV and 3.71 ± 0.08 eV, respectively, indicating their superhalogen character as these values are higher than those of halogen anions. The results may be useful for understanding the properties of gold at the nanoscale that play an important role in catalysis and nanotechnology., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

We conducted gas phase anion photoelectron spectroscopy and density functional theory studies on a number of gold acetylide species, such as AuC 2 H, AuC 2 Au, and Au 2 C 2 H. Based on the photoelectron spectra, the electron affinities of AuC 2 H, AuC 2 Au, and Au 2 C 2 H are measured to be 1.54(±0.04), 1.60(±0.08), and 4.23(±0.08) eV, respectively. The highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps of AuC 2 H and AuC 2 Au are measured to be about 2.62 and 2.48 eV, respectively. It is interesting that photoelectron spectra of AuC 2 H - and AuC 2 Au - display similar spectral features. The comparison of experimental and theoretical results confirms that the ground-state structures of AuC 2 H - , AuC 2 Au - , and their neutrals are all linear with Au-C≡C-H and Au-C≡C-Au configurations. The similar geometric structures, spectral features, HOMO-LUMO gaps, and chemical bonding between AuC 2 H -/0 and AuC 2 Au -/0 demonstrate that Au atom behaves like H atom in these species. The photoelectron spectrum of Au 2 C 2 H - shows that Au 2 C 2 H has a high electron affinity of 4.23(±0.08) eV, indicating Au 2 C 2 H is a superhalogen. Further, we found an unusual similarity between the terminal Au atom of Au 2 C 2 H - and the iodine atom of IAuC 2 H - .

The anionic silicon clusters doped with three boron atoms, B 3 Si n - (n = 4-10), have been generated by laser vaporization and investigated by anion photoelectron spectroscopy. The vertical detachment energies (VDEs) and adiabatic detachment energies (ADEs) of these anionic clusters are determined. The lowest energy structures of B 3 Si n - (n = 4-10) clusters are globally searched using genetic algorithm incorporated with density functional theory (DFT) calculations. The photoelectron spectra, VDEs, ADEs of these B 3 Si n - clusters (n = 4-10) are simulated using B3LYP/6-311+G(d) calculations. Satisfactory agreement is found between theory and experiment. Most of the lowest-energy structures of B 3 Si n - (n = 4-10) clusters can be derived by using the squashed pentagonal bipyramid structure of B 3 Si 4 - as the major building unit. Analyses of natural charge populations show that the boron atoms always possess negative charges, and that the electrons transfer from the 3s orbital of silicon and the 2s orbital of boron to the 2p orbital of boron. The calculated average binding energies, second-order differences of energies, and the HOMO-LUMO gaps show that B 3 Si 6 - and B 3 Si 9 - clusters have relatively high stability and enhanced chemical inertness. In particular, the B 3 Si 9 - cluster with high symmetry (C 3v ) stands out as an interesting superatom cluster with a magic number of 40 skeletal electrons and a closed-shell electronic configuration of 1S 2 1P 6 1D 10 2S 2 2P 6 1F 14 for superatom orbitals.

The entrance channel potentials of the prototypical polyatomic reaction family X + CH(4) → HX + CH(3) (X = F, Cl, Br, I) are investigated using anion photoelectron spectroscopy and high-level ab initio electronic structure computations. The pre-reactive van der Waals (vdW) wells of these reactions are probed for X = Cl, Br, I by photodetachment spectra of the corresponding X(-)-CH(4) anion complex. For F-CH(4), a spin-orbit splitting (∼1310 cm(-1)) much larger than that of the F atom (404 cm(-1)) was observed, in good agreement with theory. This showed that in the case of the F-CH(4) system the vertical transition from the anion ground state to the neutral potentials accesses a region between the vdW valley and transition state of the early-barrier F + CH(4) reaction. The doublet splittings observed in the other halogen complexes are close to the isolated atomic spin-orbit splittings, also in agreement with theory., (© 2011 American Institute of Physics.)

The electronic structures of CuBO(2)(-), Cu(BO(2))(2)(-), Cu(2)(BO(2))(-), and Cu(2)(BO(2))(2)(-) clusters were investigated using photoelectron spectroscopy. The measured vertical and adiabatic detachment energies of these clusters revealed unusual properties of Cu(BO(2))(2) cluster. With an electron affinity of 5.07 eV which is larger than that of its BO(2) superhalogen (4.46 eV) building-block, Cu(BO(2))(2) can be classified as a hyperhalogen. Density functional theory based calculations were carried out to identify the ground state geometries and study the electronic structures of these clusters. Cu(BO(2)) and Cu(BO(2))(2) clusters were found to form chainlike structures in both neutral and anionic forms. Cu(2)(BO(2)) and Cu(2)(BO(2))(2) clusters, on the other hand, preferred a chainlike structure in the anionic form but a closed ringlike structure in the neutral form. Equally important, substantial differences between adiabatic detachment energies and electron affinities were found, demonstrating that correct interpretation of the experimental photoelectron spectroscopy data requires theoretical support not only in determining the ground state geometry of neutral and anionic clusters, but also in identifying their low lying isomers., (© 2011 American Institute of Physics.)

Small titanium-aluminum oxide clusters, TiAlO(y) (-) (y=1-3) and TiAl(2)O(y) (-) (y=2-3), were studied by using anion photoelectron spectroscopy. The adiabatic detachment energies of TiAlO(y) (-) (y=1-3) were estimated to be 1.11±0.05, 1.70±0.08, and 2.47±0.08eV based on their photoelectron spectra; those of TiAl(2)O(2) (-) and TiAl(2)O(3) (-) were estimated to be 1.17±0.08 and 2.2±0.1eV, respectively. The structures of these clusters were determined by comparison of density functional calculations with the experimental results. The structure of TiAlO(-) is nearly linear with the O atom in the middle. That of TiAlO(2) (-) is a kite-shaped structure. TiAlO(3) (-) has a kite-shaped TiAlO(2) unit with the third O atom attaching to the Ti atom. TiAl(2)O(2) (-) has two nearly degenerate Al-O-Ti-O-Al chain structures that can be considered as cis and trans forms. TiAl(2)O(3) (-) has two low-lying isomers, kite structure and book structure. The structures of these clusters indicate that the Ti atom tends to bind to more O atoms.

The equilibrium structure, stability, and electronic properties of the Al(13)X (X=H,Au,Li,Na,K,Rb,Cs) clusters have been studied using a combination of photoelectron spectroscopy experiment and density functional theory. All these clusters constitute 40 electron systems with 39 electrons contributed by the 13 Al atoms and 1 electron contributed by each of the X (X=H,Au,Li,Na,K,Rb,Cs) atom. A systematic study allows us to investigate whether all electrons contributed by the X atoms are alike and whether the structure, stability, and properties of all the magic clusters are similar. Furthermore, quantitative agreement between the calculated and the measured electron affinities and vertical detachment energies enable us to identify the ground state geometries of these clusters both in neutral and anionic configurations.

We investigated Al(n)S(-) (n=3-15) and Al(n)S(2)(-) (n=7-15) clusters with mass spectrometry and photoelectron spectroscopy. We found that Al(13) is relatively robust when it reacts with sulfur atoms, indicating that it has some superatomic character. However, Al(13) cannot be simply considered as a superatom when it interacts with sulfur due to the following reasons: Al(13)'s icosahedral structure has been distorted slightly by sulfur atoms; the vertical detachment energies and adiabatic detachment energies of Al(13)S(-) and Al(13)S(2)(-) clusters are not significantly different from those of their neighboring clusters; and the charge distributions in Al(13)S(-) and Al(13)S(2)(-) do not necessarily associate with superatomic behavior of Al(13).

We conducted a study of Fe(n)BO(2)(-) clusters by mass spectrometry and photoelectron spectroscopy. The vertical detachment energies and adiabatic detachment energies of these clusters were evaluated from their photoelectron spectra. We have also performed density-functional calculations of Fe(n)BO(2)(-) (n=1-5) clusters and determined their structures by comparison of theoretical calculations to experimental results. The studies show that BO(2) moiety still maintains its linear structure as the bare BO(2) cluster. BO(2) behaves as a superhalogen. Analysis of molecular orbitals reveals that the highest occupied molecular orbitals of Fe(n)BO(2)(-) clusters are mainly localized on the Fe(n) units.

Betaine is a permanent zwitterion. The molecular betaine anion has been generated in a hybrid, infrared desorption-electron photoemission source and its photoelectron spectrum recorded. The photoelectron spectrum of the betaine anion is characteristic of a dipole bound anion, and its vertical detachment energy was measured to be 0.29+/-0.03 eV. Calculations by Rak, Skurski, and Gutowski [J. Chem. Phys. 114, 10673 (2001)] had found the betaine anion to be a dipole bound anion with a vertical detachment energy of 0.28 eV. We also measured the vertical detachment energy of deprotonated betaine to be approximately 1.9 eV.

The arginine parent anion was generated by a newly developed, infrared desorption-electron photoemission hybrid anion source. The photoelectron spectrum of the arginine anion was recorded and interpreted as being due to dipole binding of the excess electron. The results are consistent with calculations by Rak, Skurski, Simons, and Gutowski, who predicted the near degeneracy of arginine's canonical and zwitterionic dipole bound anions. Since neutral arginine's zwitterion is slightly less stable than its canonical form, this work also demonstrates the ability of an excess electron to stabilize a zwitterion, just as ions and solvent molecules are already known to do.