Xi-Ling Xu

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.

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.

Photofragment translational spectroscopy of n-C3H7I and i-C3H7I near 280 and 304 nm.

The photodissociation dynamics of propyl iodides n-C3H7I and i-C3H7I near 280 and 304 nm has been investigated with our mini-TOF photofragment translational spectrometer. When a single laser is applied for both the photodissociation of parent molecules and the REMPI of I atom photofragments, the TOF spectra of photofragments I*(2P1/2) and I (2P3/2) are obtained at four different wavelengths for these two iodides. For n-C3H7I, some small vibrational peaks are partially resolved (with separation of approximately 522 cm-1, corresponding to the RCH2 deformation frequency of the fragment n-C3H7) at 281.73, 279.71, and 304.67 nm. These results show that the RCH2 deformation is mostly excited. For i-C3H7I, we obtain some partially resolved vibrational peaks (with separation of approximately 352 cm-1, corresponding to the HC(CH3)2 out-of-plane bending frequency of the fragment i-C3H7) at 281.73 nm only. For n-C3H7I, the partitioning values of the available energy Eint/Eavl are 0.48 at 281.73 nm and 0.49 at 304.02 nm for the I* channel, and 0.52 at both 279.71 and 304.67 nm for the I channel. These energy partitioning values are comparable with the previous results at different wavelengths in the literature. For i-C3H7I, the Eint/Eavl values are 0.61 at 281.73 nm, 0.65 at 304.02 nm for the I* channel, and 0.62 at 279.71 nm, 0.49 at 304.67 nm for the I channel. The potential-energy-surface crossing and the beta values have also been discussed.

Structural Evolution and Electronic Properties of VnC20/– and VnC40/– (n = 1–6) Clusters: Insights from Photoelectron Spectroscopy and Theoretical Calculations

The structural evolution and electronic properties of VnC2(-/0) and VnC4(-/0) (n = 1-6) clusters were investigated using photoelectron spectroscopy and density functional theory calculations. The adiabatic and vertical detachment energies of VnC2(-) and VnC4(-) (n = 1-6) clusters were obtained from their photoelectron spectra. The most stable structures were identified by comparing the results of our calculations with the experimental data. We found that the carbon atoms of VnC2(-/0) and VnC4(-/0) (n = 1-6) clusters were separated gradually with increasing number of vanadium atoms. For VnC2(-/0) (n = 3-6) and VnC4(-/0) (n = 4-6) clusters, the carbon atoms are separated by the vanadium atoms. The geometry of V4C4 is a cubic structure and the geometries of V5C4 and V6C4 are formed by one and two vanadium atoms capping the cubic V4C4 structure, respectively.

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.

Theoretical and REMPI spectroscopic study on phenylhydrazine and phenylhydrazine–(Ar)n (n = 1, 2) van der Waals complexes

Phenylhydrazine and its van der Waals complexes with one or two argon atoms were investigated with theoretical calculations and resonant two photon ionization (R2PI) spectroscopy. The ab initio and DFT calculations found a conversion of the orbital hybridization of the Nbeta atom from sp3-like in the S0 state to sp2-like in the S1 state, suggesting that the lone pair electrons of the Nbeta atom are involved in a super p-p-pi conjugation over the skeleton of phenylhydrazine in the S1 state. The structural change of the hydrazino group in the S1<--S0 electronic transition was reflected by the vibrational excitations of the hydrazino group observed in the 1C-R2PI spectrum. The band origin of the S1<--S0 transition is determined to be 33610 cm(-1) and the adiabatic ionization energy (IE) of phenylhydrazine, measured by 2C-R2PI spectroscopy, is 62829+/-15 cm(-1). The S1<--S0 electronic transitions of phenylhydrazine-Ar and phenylhydrazine-Ar2 complexes were also observed in the 1C-R2PI spectrum, and their band origins are, respectively, red-shifted by 39 and 80 cm(-1) from that of phenylhydrazine.

Gas phase anion photoelectron spectroscopy and theoretical investigation of gold acetylide species

We conducted gas phase anion photoelectron spectroscopy and density functional theory studies on a number of gold acetylide species, such as AuC2H, AuC2Au, and Au2C2H. Based on the photoelectron spectra, the electron affinities of AuC2H, AuC2Au, and Au2C2H 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 AuC2H and AuC2Au are measured to be about 2.62 and 2.48 eV, respectively. It is interesting that photoelectron spectra of AuC2H- and AuC2Au- display similar spectral features. The comparison of experimental and theoretical results confirms that the ground-state structures of AuC2H-, AuC2Au-, 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 AuC2H-/0 and AuC2Au-/0 demonstrate that Au atom behaves like H atom in these species. The photoelectron spectrum of Au2C2H- shows that Au2C2H has a high electron affinity of 4.23(±0.08) eV, indicating Au2C2H is a superhalogen. Further, we found an unusual similarity between the terminal Au atom of Au2C2H- and the iodine atom of IAuC2H-.

Structures and chemical bonding of B3O3−/0 and B3O3H−/0: A combined photoelectron spectroscopy and first-principles theory study

We present a combined photoelectron spectroscopy and first-principles theory study on the structural and electronic properties and chemical bonding of B3O3 (-/0) and B3O3H(-/0) clusters. The concerted experimental and theoretical data show that the global-minimum structures of B3O3 and B3O3H neutrals are very different from those of their anionic counterparts. The B3O3 (-) anion is characterized to possess a V-shaped OB-B-BO chain with overall C2 v symmetry (1A), in which the central B atom interacts with two equivalent boronyl (B≡O) terminals via B-B single bonds as well as with one O atom via a B=O double bond. The B3O3H(-) anion has a Cs (2A) structure, containing an asymmetric OB-B-OBO zig-zag chain and a terminal H atom interacting with the central B atom. In contrast, the C2 v (1a) global minimum of B3O3 neutral contains a rhombic B2O2 ring with one B atom bonded to a BO terminal and that of neutral B3O3H (2a) is also of C2 v symmetry, which is readily constructed from C2 v (1a) by attaching a H atom to the opposite side of the BO group. The H atom in B3O3H(-/0) (2A and 2a) prefers to interact terminally with a B atom, rather than with O. Chemical bonding analyses reveal a three-center four-electron (3c-4e) π hyperbond in the B3O3H(-) (2A) cluster and a four-center four-electron (4c-4e) π bond (that is, the so-called o-bond) in B3O3 (1a) and B3O3H (2a) neutral clusters.

Photoelectron spectroscopy and ab initio calculations of small SinSm− (n = 1,2; m = 1–4) clusters

Binary cluster anions composed of silicon and sulfur elements, SinSm(-) (n = 1,2; m = 1-4), were investigated by using photoelectron spectroscopy and ab initio calculations. The vertical detachment energies and the adiabatic detachment energies of these clusters were obtained from their photoelectron spectra. The electron affinity of SiS molecule is determined to be 0.477 ± 0.040 eV. The results show that the most stable structures of the anionic and neutral SinSm (n = 1,2; m = 1-4) clusters prefer to adopt planar configurations except that the structures of Si2S4(-) and Si2S2 are slightly bent.

Microsolvation of sodium acetate in water: Anion photoelectron spectroscopy and ab initio calculations

To understand the microsolvation of sodium acetate (CH3COONa, NaOAc) in water, we studied NaOAc(H2O)n(-) (n = 0-3) clusters by photoelectron spectroscopy. We also investigated the structures of NaOAc(H2O)n(-) (n = 0-5) anions and NaOAc(H2O)n (n = 0-7) neutrals by quantum chemistry calculations. By comparing the theoretical results with the photoelectron experiment, the most probable structures of NaOAc(H2O)n(-/0) (n = 0-3) were determined. The study also shows that, with increasing n, the solvent-separated ion pair (SSIP) structures of NaOAc(H2O)n(-) anions become nearly energetically degenerate with the contact ion pair (CIP) structures at n = 5, while the SSIP structures of the neutral NaOAc(H2O)n clusters appear at n = 6 and become dominant at n = 7.