Xiang-Yu Kong

Structures and magnetic properties of CrSin− (n = 3–12) clusters: Photoelectron spectroscopy and density functional calculations

Chromium-doped silicon clusters, CrSi(n)(-) (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 CrSi(n)(-) clusters occurs at n = 10 and the magnetic properties of the CrSi(n)(-) clusters are correlated to their geometric structures. The most stable isomers of CrSi(n)(-) from n = 3 to 9 have exohedral structures with magnetic moments of 3-5μ(B) while those of CrSi(10)(-), CrSi(11)(-), and CrSi(12)(-) have endohedral structures and magnetic moments of 1μ(B).

Structural and Magnetic Properties of CoGen− (n=2–11) Clusters: Photoelectron Spectroscopy and Density Functional Calculations

A series of cobalt-doped germanium clusters, CoGe(n)(-/0) (n=2-11), are investigated by using anion photoelectron spectroscopy combined with density functional theory calculations. For both anionic and neutral CoGe(n) (n=2-11) clusters, the critical size of the transition from exo- to endohedral structures is n=9. Natural population analysis shows that there is electron transfer from the Ge(n) framework to the Co atom at n=7-11 for both anionic and neutral CoGe(n) clusters. The magnetic moments of the anionic and neutral CoGe(n) clusters decrease to the lowest values at n=10 and 11. The transfer of electrons from the Gen framework to the Co atom and the minimization of the magnetic moments are related to the evolution of CoGe(n) structures from exo- to endohedral.

Smallest fullerene-like silicon cage stabilized by a V2 unit

We conducted a combined anion photoelectron spectroscopy and density functional theory study on V2Si20 cluster. Our results show that the V2Si20 cluster has an elongated dodecahedron cage structure with a V2 unit encapsulated inside the cage. It is the smallest fullerene-like silicon cage and can be used as building block to make cluster-assembled materials, such as pearl-chain style nanowires.

Anion Photoelectron Spectroscopy and Density Functional Study of Small Aluminum-Vanadium Oxide Clusters

Small aluminum-vanadium oxide clusters, AlVO(y)(-) (y = 1-3) and Al(x)VO(2)(-) (x = 2, 3), were investigated with anion photoelectron spectroscopy and density functional calculations. The adiabatic detachment energies of AlVO(y)(-) were estimated to be 1.06 ± 0.05, 1.50 ± 0.08, and 2.83 ± 0.08 eV for y = 1, 2, and 3. Those of Al(2)VO(2)(-) and Al(3)VO(2)(-) were estimated to be 1.22 ± 0.08 and 1.25 ± 0.08 eV. Comparison of theoretical calculations with experimental measurement suggests that the most probable structure of AlVO(-) cluster is quasilinear with O atom in the middle. AlVO(2)(-) has an irregular chain structure of Al-O-V-O and a C(2v) cyclic structure very close in energy. The structure of AlVO(3)(-) cluster is evolved from the C(2v) cyclic AlVO(2)(-) structure by adding the third O atom to the V atom. Al(2)VO(2)(-) has a pair of nearly degenerate Al-O-V-O-Al chain structures that can be considered as cis and trans forms. Al(3)VO(2)(-) probably has two low-lying isomers each containing a four-membered ring. The structures of the corresponding neutral clusters are discussed.

Vibrationally Resolved Photoelectron Spectroscopy of the Model GFP Chromophore Anion Revealing the Photoexcited S1 State Being Both Vertically and Adiabatically Bound against the Photodetached D0 Continuum

The first excited state of the model green fluorescence protein (GFP) chromophore anion (S1) and its energy level against the electron-detached neutral radical D0 state are crucial in determining the photophysics and the photoinduced dynamics of GFP. Extensive experimental and theoretical studies, particularly several very recent gas-phase investigations, concluded that S1 is a bound state in the Franck-Condon vertical region with respect to D0. However, what remains unknown and challenging is if S1 is bound adiabatically, primarily due to lack of accurate experimental measurements as well as due to the close proximity in energy for these two states that even sophisticated high-level ab initio calculations cannot reliably predict. Here, we report a negative ion photoelectron spectroscopy study on the model GFP chromophore anion, the deprotonated p-hydroxybenzylidene-2,3-dimethylimidazolinone anion (HBDI(-)) taken under low-temperature conditions with improved energy resolution. Despite the considerable size and low symmetry of the molecule, resolved vibrational structures were obtained with the 0-0 transition being the most intense peak. The adiabatic (ADE) and vertical detachment (VDE) energies therefore are determined both to be 2.73 ± 0.01 eV, indicating that the detached D0 state is 0.16 eV higher in energy than the photon excited S1 state. The accurate ADE and VDE values and the well-resolved photoelectron spectra reported here provide much needed robust benchmarks for future theoretical investigations.

Photoelectron spectroscopy and density functional calculations of AgSin− (n = 3–12) clusters

We investigated the structural evolution and electronic properties of AgSi(n)(-) (n = 3-12) clusters using anion photoelectron spectroscopy and density functional theory calculations. The vertical detachment energies and adiabatic detachment energies of AgSi(n)(-) (n = 3-12) clusters were estimated from their photoelectron spectra. The structures of the AgSi(n)(-) (n = 3-12) clusters were tentatively assigned based on the comparison of theoretical calculations and experimental measurements. The studies show that the structures of AgSi(n)(-) (n = 3-12) clusters are dominated by exohedral structures with the Ag atom occupying the low coordinated sites. No endohedral structure has been found for AgSi(n)(-) clusters with n ≤ 12.

Anomalous Property of Ag(BO2)2 Hyperhalogen: Does Spin–Orbit Coupling Matter?

Hyperhalogens were recently identified as a new class of highly electronagative species which are composed of metals and superhalogens. In this work, high-level theoretical calculations and photoelectron spectroscopy experiments are systematically conducted to investigate a series of coinage-metal-containing hyperhalogen anions, Cu(BO(2))(2)(-), Ag(BO(2))(2)(-), and Au(BO(2))(2)(-). The vertical electron detachment energy (VDE) of Ag(BO(2))(2)(-) is anomalously higher than those of Au(BO(2))(2)(-) and Cu(BO(2))(2)(-). In quantitative agreement with the experiment, high-level ab initio calculations reveal that spin-orbit coupling (SOC) lowers the VDE of Au(BO(2))(2)(-) significantly. The sizable magnitude of about 0.5 eV of SOC effect on the VDE of Au(BO(2))(2)(-) demonstrates that SOC plays an important role in the electronic structure of gold hyperhalogens. This study represents a new paradigm for relativistic electronic structure calculations for the one-electron-removal process of ionic Au(I)L(2) complexes, which is characterized by a substantial SOC effect.

Structural and bonding properties of small TiGen− (n = 2–6) clusters: photoelectron spectroscopy and density functional calculations

A number of small TiGen− (n = 2–6) clusters were investigated using anion photoelectron spectroscopy and density functional theory calculations. Their structures were determined by comparison of the theoretical vertical detachment energies and simulated spectra of the low-lying isomers with the experimental results. The most stable structure of TiGen− (n = 2–6) clusters can be considered as a Ti atom substituting one of the Ge atoms in the corresponding Gen+1 cluster or a Ti atom capping a Gen cluster. The HOMOs of TiGen− (n = 2–6) clusters are mainly localized on the Ti atom and the Ge atoms interacting directly with the Ti atom.

Structural and magnetic properties of FeGen−/0 (n = 3-12) clusters: Mass-selected anion photoelectron spectroscopy and density functional theory calculations

The structural, electronic, and magnetic properties of FeGen-/0 (n = 3-12) clusters were investigated by using anion photoelectron spectroscopy in combination with density functional theory calculations. For both anionic and neutral FeGen (n = 3-12) clusters with n ≤ 7, the dominant structures are exohedral. The FeGe8-/0 clusters have half-encapsulated boat-shaped structures, and the opening of the boat-shaped structure is gradually covered by the additional Ge atoms to form Gen cage from n = 9 to 11. The structures of FeGe10-/0 can be viewed as two Ge atoms symmetrically capping the opening of the boat-shaped structure of FeGe8, and those of FeGe12-/0 are distorted hexagonal prisms with the Fe atom at the center. Natural population analysis shows that there is an electron transfer from the Ge atoms to the Fe atom at n = 8-12. The total magnetic moment of FeGen-/0 and local magnetic moment of the Fe atom have not been quenched.