Products of the addition of water molecules to Al3O3- clusters: structure, bonding, and electron binding energies in Al3O4H2-, Al3O5H4-, Al3O4H2, and Al3O5H4

Two stable products of reactions of water molecules with the Al3O3- cluster, Al3O4H2- and Al3O5H4-, are studied with electronic structure calculations. There are several minima with similar energies for both anions and the corresponding molecules. Dissociative absorption of a water molecule to produce an anionic cluster with hydroxide ions is thermodynamically favored over the formation of Al3O3-(H2O)n complexes. Vertical electron detachment energies of Al3O4H2- and Al3O5H4- calculated with ab initio electron propagator methods provide a quantitative interpretation of recent anion photoelectron spectra. Contrasts and similarities in these spectra may be explained in terms of the Dyson orbitals associated with each transition energy.     

Synthesis of spherical silver nanoparticles by digestive ripening, stabilization with various agents, and their 3-D and 2-D superlattice formation

Capped nanoparticles of silver were synthesized via the solvated metal atom dispersion (SMAD) technique followed by a digestive ripening procedure producing gram quantities of monodisperse spherical nanoparticles. This shows for the first time that a digestive ripening protocol is possible for an element other than gold. The particle size and optical spectra were found to be dependent on the capping agent used. Particles capped with dodecane thiol had a mean diameter of 6.6+/-1 nm, while trioctyl phosphine capped particles were 6.0+/-2 nm determined via TEM microscopy. These particles were found to organize into two- and three-dimensional superlattices with a well defined geometry through self-assembly in a liquid solution, that was dictated by the ligand used resulting in a triangular or circular lattice.     

Synthesis and photochemistry of Ru(II) complexes containing phenanthroline-based ligands with fused pyrrole rings

Hydrolysis of 1,10-phenanthrolinopyrrole ethyl ester leads to the acid derivative which is unstable at room-temperature releasing CO(2) and forming 1,10-phenanthrolinopyrrole (php). The ligand reacts with ruthenium(II) to form a series of complexes of the general formula [Ru(php)(n)(bpy)(3-n)](2+), where bpy = 2,2'-bipyridine and n = 1-3. The photochemical properties reveal that the complexes have longer-lived excited states than the standard complex, [Ru(bpy)(3)](2+). Their emission lifetimes range from 9.04 micros (n = 1) to 35.5 micros (n = 3) at 77 K compared to 7.57 micros for the standard. Similarly, at room-temperature, emission lifetimes range from 1.20 micros (n = 1) to 1.70 micros (n = 3) relative to the standard (0.56 micros). The emission quantum yields also have higher values than the standard [Ru(bpy)(3)](2+) under similar conditions. The temperature-dependent studies for the complexes establish the distribution among the radiative, nonradiative, and (3)MLCT to (3)d-d decay channels and are in agreement with the energy gap law.     

Dimethyl azo(bisisobutyrate) and C(60) produce 1,4- and 1, 16-Di(2-carbomethoxy-2-propyl)-1,x-dihydro

Thermal decomposition of dimethyl azo(bisisobutyrate) in a solution containing C(60) produced 1,4- and 1, 16-di(2-carbomethoxy-2-propyl)-1,x-dihydro[60]fullerenes in yields of 21% and 27%, respectively, based on reacted C(60). The structure of this first 1,16-dialkyl-1,16-dihydro[60]fullerene was assigned from (13)C 2D INADEQUATE NMR spectra. The 1,16-isomer has first and second electrochemical reduction potentials shifted positively by 0. 18 V relative to those of the 1,4-isomer. From the close similarity of all spectral, chromatographic, and electrochemical data, the previously unassigned isomer of 1,x-di(2-cyano-2-propyl)-1, x-dihydro[60]fullerene, which was obtained from azo(bisisobutyronitrile) and C(60), is also a 1,16-isomer.     

Cooperative two-photon-induced chemical bond formation during a Kr+F2 collision to form KrF

The reactive Kr⁺F₂⁻ potential energy surface is probed by two-photon, laser-induced chemical bond formation during a Kr+F₂ collision. This is compared with the pulsed laser excitation (two-photon) of Kr(2p₉) followed by collision with F₂ leading to the formation of KrF(B, C). In addition to reporting the excitation spectrum for the two-phonon-induced collision process, these techniques were used to determine quenching rate constants of Kr₂F^*. Quenching by Xe gives XeF(B, C) with rate constant (1.5±0.2)×10⁻¹⁰ cm³ s⁻¹; the quenching rate constant for F₂ is (1.5±0.2)×10⁻¹⁰ cm³ s⁻¹, and the radiative lifetime of Kr₂F^* is 240±35 ns. The quenching rate constant for the coupled Kr(2p₈) and Kr(2p₉) levels by F₂ is (13±2)×10⁻¹⁰ cm³ s⁻¹.     

Molecular photoionization cross sections in electron propagator theory: angular distributions beyond the dipole approximation

Corrections to dipole approximation results for angular distributions in photoionization of first-row hydrides have determined by using Dyson orbitals calculated with ab initio electron propagator theory and by considering the full multipole expansion for the incident photon representation. The relative importance of first-order corrections which consist of electric quadrupole and magnetic dipole terms and of higher-order terms has been estimated as a function of photon energy. Multipole corrections to the dipole approximation depend on photon energy and on the characteristics of the Dyson orbitals.     

Excitation of XeF* by reactions of XeF2 with Ar(3P0,2),Kr(3P2) and Xe(3P2)

The reactions of the lowest metastable states of Ar, Kr and Xe with XeF₂ were studied in a flowing afterglow apparatus; XeF emission (from D²Π_{$\text{1}\text{2}$} and B ²Π⁺ states) was observed in all cases. The total rate constants (cm³ molecule^?1 s^?1) for XeF^* formation were determined as 75 × 10^?11 ? Xe(³P₂);64 × 10^?11 ? Kr(³P₂) and 20 × 10^?11 ? Ar(³P_0,2). The reactions of Ar(³P_0,2) and Kr(³P₂) with XeF₂ also gave ArF^* and KrF^*, respectively. Analysis of these emissions indicates that at least two different mechanisms are operative: reactive quenching by the ionic—covalent curve-crossing mechanism and excitation transfer. The Ar(³P_0,2 + XeF₂ reaction is a sufficiently strong source of XeF(D—X) emission that the main features of the XeF(D²Π_{$\text{1}\text{2}$} ? X²Σ⁺) system could be photographed and tentative assignments of these vibrational bands are given. The XeF(D → B) emission could not be observed and the ratio of the D—X versus the D—B transition probability must be > 1000 : 1.     

The strong fixed point property for lexicographic sums

The following theorem is proved: If Q=L{P _t tT} is a finite lexicographic sum of posets such that T and all P _t have the strong fixed point property then Q has the strong fixed point property. Moreover we show the strong fixed point property for two more classes of posets.     

Filters and supports in orthoalgebras

An orthoalgebra, which is a natural generalization of an orthomodular lattice or poset, may be viewed as a logic or proposition system and, under a welldefined set of circumstances, its elements may be classified according to the Aristotelian modalities: necessary, impossible, possible, and contingent. The necessary propositions band together to form a local filter, that is, a set that intersects every Boolean subalgebra in a filter. In this paper, we give a coherent account of the basic theory of Orthoalgebras, define and study filters, local filters, and associated structures, and prove a version of the compactness theorem in classical algebraic logic.     

2-(1-Azulyl)ethyl tosylate methylene scrambling in the gas phase. Similarities to solution chemistry

The methylene groups in 2-(1-azulyl)ethyl tosylate are largely scrambled prior to formation of fragment ions in the mass spectrometer. This process also occurs in the 3-nitro analog, where it is dependent on sample residence time in the source and independent of electron energy. It could not be observed with the isomeric 6-substituted tosylates, the 1-substituted acetates or alcohols, or with 2-(p-anisyl)ethyl tosylate. Scrambling occurs in the neutral molecule prior to ionization and a mechanism involving absorption onto the metal surface and formation of a complexed ethylenazulonium ion is suggested.