The Au(CN)(2)(-) ion is the most stable Au compound known for centuries, yet a detailed understanding of its chemical bonding is still lacking. Here we report direct experimental evidence of significant covalent bonding character in the Au-C bonds in Au(CN)(2)(-) using photoelectron spectroscopy and comparisons with its lighter congeners, Ag(CN)(2)(-) and Cu(CN)(2)(-). Vibrational progressions in the Au-C stretching mode were observed for all detachment transitions for Au(CN)(2)(-), in contrast to the atomic-like transitions for Cu(CN)(2)(-), revealing the Au-C covalent bonding character. In addition, rich electronic structural information was obtained for Au(CN)(2)(-) by employing 118 nm detachment photons. Density functional theory and high-level ab initio calculations were carried out to understand the photoelectron spectra and obtain insight into the nature of the chemical bonding in the M(CN)(2)(-) complexes. Significant covalent character in the Au-C bonding due to the strong relativistic effects was revealed in Au(CN)(2)(-), consistent with its high stability.

As a part of the COMPASS force field development, a number of small inorganic molecules were parametrized for condensed-phase applications. Using a simple valence model coupled with Coulomb energy and Lennard-Jones 9-6 functional terms, the parameters were optimized to yield accurate prediction of structural, vibrational, and thermophysical properties for these molecules. Extended validation on liquid nitrogen (N 2 ) and carbon dioxide (CO 2 ) in normal and supercritical conditions demonstrates that the present force field is capable of predicting various thermophysical properties in a very broad range of experimental conditions.

Sulfate is an important inorganic anion and its interactions with water are essential to understand its chemistry in aqueous solution. Studies of sulfate with well-controlled solvent numbers provide molecular-level information about the solute-solvent interactions and critical data to test theoretical methods for weakly bounded species. Here we report a low-temperature photoelectron spectroscopy study of hydrated sulfate clusters SO(4)(2-)(H(2)O)(n) (n = 4-7) at 12 K and ab initio studies to understand the structures and dynamics of these unique solvated systems. A significant increase of electron binding energies was observed for the 12 K spectra relative to those at room temperature, suggesting different structural isomers were populated as a function of temperature. Theoretical calculations revealed a competition between isomers with optimal water-solute and water-water interactions. The global minimum isomers all possess higher electron binding energies due to their optimal water-solute interactions, giving rise to the binding energy shift in the 12 K spectra, whereas many additional low-lying isomers with less optimal solvent-solute interactions were populated at room temperature, resulting in a shift to lower electron binding energies in the observed spectra. The current work demonstrates and confirms the complexity of the water-sulfate potential energy landscape and the importance of temperature control in studying the solvent-solute systems and in comparing calculations with experiment.

High energy photon is needed for photoelectron spectroscopy (PES) of anions with high electron binding energies, such as superhalogens and O-rich metal oxide clusters. The highest energy photon used for anion PES in the laboratory has been 157 nm (7.866 eV) from F2 eximer lasers. Here, we report an anion PES experiment using coherent vacuum ultraviolet radiation at 118.2 nm (10.488 eV) by tripling the third harmonic output (355 nm) of a Nd:YAG laser in a XeAr cell. Our study focuses on a set of superhalogen species, MCl(4) (-) (M=Sc, Y, La), which were expected to possess very high electron binding energies. While the 157 nm photon can only access the ground state detachment features for these species, more transitions to the excited states at binding energies higher than 8 eV are observed at 118.2 nm. The adiabatic detachment energies are shown to be, 6.84, 7.02, and 7.03 eV for ScCl(4) (-), YCl(4) (-), and LaCl(4) (-) eV, respectively, whereas their corresponding vertical detachment energies are measured to be 7.14, 7.31, and 7.38 eV.

Abstract. The direct excitation cross section for the atomic oxygen 3p ___> 3S0 transition (X1304•) has been measured at four incident energies between 13.4 and 40 eV. These measurements were made to add sufficient detail to previous direct excitation measurements to allow the near-threshold cross section to be determined. Previous optical measurements of the 1304fk emission cross section disagree by up to a factor of 2 in this important energy region. We have also compared the atomic hydrogen e + H(ls) --• H(2s + 2p) cross section, used previously as a secondary standard for our direct excitation measurements of atomic oxygen cross sections, to recent measurements of the total e + H --• Lyman alpha cross section and have found agreement at the _+ 15% level, making a revision of our previously reported atomic oxygen cross sections unnecessary. Previous MeasurementsAny measurement of a cross section for production of excited states of an unstable species such as atomic oxygen is a difficult experimental problem. Not only is it necessary to produce the species in reasonable density, but its abundance must be determined, either absolutely or with reference to another species also present which has an observable transition whose cross section is well enough known to be used as a secondary

A combined zero electronic kinetic energy spectroscopy and ion-pair dissociation imaging study of the

The vibrational structures of the electronic ground states ((approximately)X (2)A(2)) of furan, pyrrole, and thiophene cations have been studied by zero kinetic energy (ZEKE) photoelectron spectroscopic method. In addition to the strong excitations of the symmetric a(1) vibrational modes, other three symmetric vibrational modes (a(2), b(1), and b(2)) have been observed unambiguously. These results which cannot be explained by the Franck-Condon principle illustrate that the vibronic coupling and the Coriolis coupling may play important roles in understanding the vibrational structures of the five-membered heterocycle cations. The vibrationally resolved ZEKE spectra are assigned with the assistance of the density function theory calculations, and the fundamental frequencies for many vibrational modes have been determined for the first time. The first adiabatic ionization energies for furan, pyrrole, and thiophene were determined as 8.8863, 8.2099, and 8.8742 eV, respectively, with uncertainties of 0.0002 eV.

Spectroscopic and electrochemical investigations have been carried out on a collection of hydrogen-bonded mixed-valence adducts of ruthenium complexes. The electron donors (H-bond acceptors) are Ru(II) cyano species and the electron acceptors (H-bond donors) are Ru(III) ethylenediamine species, and NIR spectroscopic transitions in the adducts are assigned to intervalence transfer through the hydrogen bonds holding the adducts together (HBIT). Spectroscopic studies using Job's method indicate that the adducts are 2:1 ternary aggregates of formulations such as [((trpy)(bpy)RuII(CN))2,(en)2RuIII(bpy)]5+ and [((bpy)2RuII(CN)2)2,(en)2RuIII(bpy)]3+. Voltammetric investigations show substantial repulsion of the redox waves of the parent complexes in mixtures containing both donor and acceptor. Comparison with known electronic coupling data for mixed-valence ruthenium dimers covalently bound through dithiaspiroalkane bridging ligands indicates that the electronic coupling through H bonds of this type is 65−75% as strong as through σ-covalent bonds.