Electron emission in slow collisions of K+ ions with alkalated (K,Cs) W(110) surfaces

We have investigated K⁺ collisions (200 to 1000 eV) under grazing incidence with partially alkalated (K, Cs) W(110) surfaces by energy analysis of the ejected electrons. Three different mechanisms for electron emission could be identified (1) Kinetic emission mainly confined to projectile energies greater than 300 eV, (2) Auger deexcitation of excited projectile valence states yielding electrons with energies up to about 2.9 eV and (3) Creation of inner shell vacancies (Cs(5p ^?1) and K(3p ^?1)) which gives rise to Auger type processes (OVV and MVV) and to the formation of autoionizing states of the type A (np ⁵ n′s n″l) (A=Alkali atom). The relative importance of the three mechanisms is studied as a function of the alkali coverage of the surface and of the projectile's energy.     

Ionic Mobility in Glasses in the ZrF4-BiF3-MF Systems (M = Li,Na, K) as Probed by 7Li, 19F,and 23Na NMR

The ion mobility in new fluoride glasses (mol %) 45ZrF₄ · 25BiF₃ · 30MF (I) (M = Li, Na, K), (70 - x)ZrF₄ · xBiF₃ · 30LiF (II) (15 ≤ x ≤ 35), and 45ZrF₄ · (55-x)BiF₃ · xMF (III) (M = Li, Na; 10 ≤ x ≤ 30) has been studied by ⁷Li, ¹9F, and ²³Na NMR in the temperature range 250–500 K. The character of ion motion in bismuth fluorozirconate glasses I and III is determined by temperature and the nature and concentration of an alkali-metal cation. Major type of ion mobility in glasses I–III at temperature 400–440 K are local motions of fluorine-containing moieties and diffusion of lithium ions (except for the glass with x = 10). The factors responsible for diffusion in the fluoride sublattice of glasses I have been determined. Sodium ions in glasses I and III are not involved in ion transport.     

Bromo dimethyl sulfoxide osmium(II) complexes. Molecular structure of cis,fac-[OsBr2(dmso-S)3(dmso-O)]

Bromo dimethyl sulfoxide osmium(II) complexes were synthesized: trans-[OsBr₂(dmso-S)₄] (1) was obtained by the reaction of K₂[OsBr₆] with DMSO in the presence of SnBr₂ at 100°C and cis,fac-[OsBr₂(dmso-S)₃(dmso-O)] (2) was prepared by thermal isomerization of 1 in a DMSO solution at 150°C. The coordination mode of DMSO molecules was determined by IR and ¹H and ¹³C NMR spectroscopy. X-ray diffraction analysis showed that compound 2 crystallizes in the monoclinic system, space group P2₁/n; a = 8.4711(5) Å, b = 27.7876(15) Å, c = 8.5569(5) Å, β = 115.7110(10)°; Z = 4. The coordination polyhedron of osmium is a distorted octahedron; the osmium environment is formed by two cis-arranged bromine atoms and three fac-S-coordinated and one O-coordinated DMSO molecules. The interconversion of complexes in solutions was studied by UV/Vis and ¹H and ¹³C NMR spectroscopy. In chloroform and DMSO, complex 2 isomerizes to cis-[OsBr₂(dmso-S)₄] and (in the light) to 1. The complexes trans-[OsX₂(dmso-d₆)₄], where X = Cl, Br, were isolated from DMSO-d ₆ and characterized by the IR spectra.     

Intra- and inter-atomic auger processes in collisions of low energy He++, He+, He* (23,S, 21 S) and Li+ with Li covered W(110) surfaces

Electron spectra from He⁺⁺, He⁺ and Li⁺ (10 to 1500 eV) ions colliding under grazing incidence with Li covered W (110) surfaces are reported. The results are compared with those obtained from thermal collisions of (2³ S; 2¹ S) metastable He atoms. In these collisions 1s vacancies are either produced during the collision event (energetic He⁺ (Li ⁺) collisions) or are brought into the collision (slow He⁺⁺ (He⁺, He*) collisions). Population of the 2s orbitals by two electrons produces states which decay by intraatomic Auger processes: we observe autoionization of He** (2s ²) and Li** (1s 2s ²) as well as autodetachment of He^?* (1s 2s ²). Alternatively the 1s-holes in the projectile or target (Li) can be filled by Auger processes involving one or two surface electrons. The processes leading to electron emission are studied as a function of the Li coverage in the submonolayer region (0≦Θ_Li≦1Ml) and as a function of the projectile energy. It is concluded that with one or two 1s vacancies present in the projectile the double capture of two surface electrons constitutes an important process responsible for electron emission of low work function surfaces.     

Variational grand-canonical electronic structure of Li+Li at ~10<Superscript>4</Superscript> K with second-order perturbation theory corrections

An ab initio variational grand-canonical electronic structure mean-field method, based on the Gibbs–Peierls–Bogoliubov minimum principle for the Gibbs free energy, is applied to the di-lithium (Li+Li) system at temperatures around T ≈ 10⁴ K and electronic chemical potential of μ ≈ ?0.1E _h . The method is an extension of the Hartree–Fock approach to finite temperatures. We first study the Li₂ molecule at a frozen inter-nuclear distance of R = 3 Å as a function of temperature. The mean-field electronic structure changes smoothly as temperature increases, up to 10⁴ K, where a sharp spontaneous spin-polarization emerges as the variational mean-field solution. Further increase in the temperature extinguishes this polarization. We analyze the mean-field behavior using a correlated single-site Hubbard model and show it arises from an attempt of the mean-field to mimic the polarization of the spin–spin correlation function of the exact solution. Next, we keep constant the temperature at 10⁴ K and examine the electronic structure as a function of inter-nuclear distance R. At R = 3.7 Å, a crossing between two free energy states occurs: One state is “spin-unpolarized” (becomes lower in energy when R > 3.7 Å), while the other is “spin polarized”. This crossing causes near-discontinuous jumps in calculated properties of the system and is associated with using the noninteracting electron character of our mean-field approach. Such problems will likely plague FT-DFT calculations as well. We use second-order perturbation theory (PT2) to study effects of electron correlation on the potential of mean force between the two colliding Li atoms. We find that PT2 correlation free energy at ~10⁴ K is larger than at 0 K and tends to restore the spin-polarized state as the lowest free energy solution.     

Electron emission in collisions of slow rare gas ions with partially cesiated W (110)

We report the spectra of electrons emitted after slow collisions (50 eV) of rare gas ions (He⁺, Ne⁺, Ar⁺, and Xe⁺) with partially cesiated W(110) surfaces. The electron spectra are discussed in terms of the two interatomic Auger processes, Auger Capture and Auger Deexcitation and the intra-atomic Auger process, Autodetachment of Rg^–* (He^–* (1s 2s ^{2 2} S) in the case of He). Model calculations including these processes can qualitatively reproduce the measured spectra as well as experimental values for the electron emission coefficients, . This is demonstrated for collisions of He⁺ ions and thermal metastable He atoms with clean and partially cesiated W(110).     

PET imaging of sterile inflammation with a 18F-labeled bis(zinc(II)-dipicolylamine) complex

Small-molecular probe ¹⁸F-labeled bis(zinc(II)-dipicolylamine) complex (¹⁸F-FB-DPAZn2) was evaluated for PET imaging of sterile inflammation. In comparison with ¹⁸F-2-deoxy-β-d-glucose (¹⁸F-FDG), ¹⁸F-radiolabeled Annexin V (¹⁸F-FB-Annexin V) showed rapid clearance of radioactivity from the kidney and low uptake in most tissues. Both the lower radioactivity accumulation in brain and heart and the higher uptakes in the lung, liver, and intestine were observed for the biodistribution of ¹⁸F-FB-DPAZn2. In PET imaging, ¹⁸F-FDG showed significantly higher tumor and inflammation uptake than did of ¹⁸F-FB-DPAZn2 and ¹⁸F-FB-Annexin V in the S-180 fibrosarcoma mouse model and sterile inflammation mouse model. Both ¹⁸F-FB-DPAZn2 and ¹⁸F-FB-Annexin V performed the specifically localization in inflammation, and the ratios of inflammatory lesion-to-muscle and tumor-to-muscle were 1.83 ± 0.20 and 0.90 ± 0.12 (P < 0.05) for ¹⁸F-FB-DPAZn2, and 1.51 ± 0.14 and 1.21 ± 0.12 (P > 0.05) for ¹⁸F-FB-Annexin V, respectively. Terminal deoxynucleotide end-labeling (TUNEL) assays performed on the dissected tissues showed the significantly more TUNEL-positive nuclei in the inflammatory muscle than in tumor and normal muscle, and these TUNEL results correlated with the uptake of ¹⁸F-FB-DPAZn2 in dissected tissues. Biodistribution and PET imaging studies showed that the ¹⁸F-FB-DPAZn2 is suitable for imaging sterile inflammation in vivo and is capable of the differentiating tumor from inflammation.     

Time spectroscopy in theA 1∑ u + state of Li2

We have determined effective cross-sections for resonant transfer of excitation energy from state-selected Li₂ molecules to ground state Li atoms $$Li_2 A\left( {\upsilon ',J'} \right) + Li2S \to Li_2 X\left( {\upsilon '',J''} \right) + Li2P$$ with two different experimental techniques. Absolute cross-sections were derived from lifetime measurements of 114 rotational levels of theA-state subject to resonant collisions which belong to vibrational statesv′=4, 5, 6, 7 and 11 of⁶Li₂ and⁷Li₂. Cross-sections amount to several thousand Ų dropping off sharply with a resonance half-width of about 16 cm^?1. The resonance behaviour of the collision cross-section inferred from lifetime data could be confirmed by a double resonance technique probing the number of excited atoms with a second laser while the first laser was scanned over the Li₂ X?A absorption band. Due to their high reliability our data prove a good basis for the test of theoretical models. In contrast to earlier investigations significant deviations were found to exist between the measured cross-sections and those predicted by the first-order dipole-dipole scattering theory.     

Lithiumtriamidostannat(II), Li[Sn(NH2)3] – Synthese und Kristallstruktur

Lithium Triamidostannate(II), Li[Sn(NH₂)₃] – Synthesis and Crystal Structure Rusty-red glistening, transparent crystals of Li[Sn(NH₂)₃] were obtained by reaction of metallic lithium with tetraphenyl tin in liquid ammonia at 110 °C. The structure was determined from X-ray single-crystal diffractometer data: Space group P 2₁/n, Z = 4, a = 8.0419(9) Å, b = 7.1718(8) Å, c = 8.5085(7) Å, β = 90.763(8)°, R₁ (F _o ≥ 4σ(F _o)) = 2.8%, wR₂ (F ≥ 2σ(F )) = 5.3%, N(F ≥ 2σ(F )) = 1932, N(Var.) = 65. The crystal structure contains trigonal pyramidal complex anions [Sn(NH₂)₃]^– with tin at the apex, which are connected to layers of sequence A B A B … by lithium in tetrahedra-double units [Li(NH₂)_2/2(NH₂)₂]₂.     

On the determination of HCl+ (A,v′) vibrational populations from HCl+ (A→X) fluorescence spectra: direct comparison between photoionization and penning ionization

Using a beam apparatus, we have measured the HCl⁺ (A,v′→X,v″) fluorescence spectra of HCl⁺ (A,v′) ions formed in HeI (58.4 nm), and NeI (73.6 nm) photoionization and, for the first time, in He (2³ S) Penning ionization under single collision conditions with a wavelength bandwidth around 1 nm. In addition, we have studied Ne (3s ³ P _{2, 0}) Penning ionization of HCl at three different collision energies. The procedure and the problems in extracting HCl⁺ (A,v′) vibrational populations from the data are discussed in some detail. Thedirect comparison of photoionization and Penning ionization data allows definitive conclusions to be drawn on the question whether final state interactions in the Penning reaction change the “nascent” vibrational population (determined by electron spectrometry); for He (2³ S)+HCl, such changes are shown to be absent within the experimental uncertainty (<±10%). For Ne (3s ³ P _{2, 0})+HCl, the HCl⁺ (A,v′=0, 1) populations are also found to be close to those measured by electron spectrometry and essentially independent of collision energy in the range 34–96 meV. From measurements of the fluorescence intensity as a function of HCl density, we have evidence for a fast loss of HCl⁺ (A,v′) ions in collisions with HCl (rate constant around 5·10^?9 cm³s^?1).     

The Effect of O6+ and Si7+ ion beam irradiations on poly(lactide-co-glycolide) (50: 50) copolymer

Sterilization by ion beam radiations unfortunately also has a significant effect on the degradation of many polymers. The aim of present study is to examine the effect of heavy ion beam irradiation on poly(lactide-co-glycolide) (PLGA) (50: 50). The radiation effect is manifested through its degradation behavior and changes in the morphological, optical and structural properties. PLGA films are prepared by solvent casting method and subsequently irradiated with swift heavy ions O⁶⁺ and Si⁷⁺ ion with fluence in the range of 5 × 10¹⁰?1 × 10¹² ions/cm². The dominant effect on PLGA films is chain scission as evidenced by change in surface modification. Changes in optical and structural properties were analyzed by UV-Vis, XRD and FTIR spectrometric techniques. XRD technique is not responsive to degradation occurring in samples. Surface modifications caused by ion irradiations have been observed with SEM.     

Polymeric lithium(I) diaquabarbiturate: Crystal structure

The lithium(I) catena-diaquabarbiturate complex [Li(H₂O)₂(HBA–O,O′)] _n (I), where Н₂ВА is barbituric acid, has been structurally characterized by X-ray diffraction (CIF file CCDC no. 1447689), and its thermal decomposition and IR spectrum have been studied. Crystals of complex I are monoclinic, a = 6.4306(7) Å, b = 16.720(1) Å, c = 7.1732(8) Å, β = 108.253(4)°, V = 732.5(1) ų, space group P2₁/c, and Z = 4. One independent μ₂-bridging HBA^– ligand is coordinated to two Li(I) ions via the two oxygen atoms of C₄₍₆₎=O carbonyl groups. Each Li⁺ ion is linked with two μ₂-HBA^– ions and two terminal water molecules at tetrahedron vertices. μ₂-HBA^– ions link tetrahedra into a chain. The structure is stabilized by multiple hydrogen bonds and π–π-interaction between HBA^–. The shift of ν(C=O) vibration bands in the IR spectrum of complex I in comparison with Н₂ВА towards lower frequencies agrees with the coordination of HBA^– via oxygen atoms. The dehydration of complex I occurs in two stages in the regions of 100–150 and 150–240°C.     

X-Ray diffraction data for new ferrites ErMFe<Subscript>2</Subscript>O<Subscript>5</Subscript> (M = Li,Na, K)

New ferrites ErMFe₂O₅ (M = Li, Na, K) were synthesized from erbium and iron(III) oxides and lithium, sodium, and potassium carbonates by solid-state annealing. According to X-ray powder diffraction, these compounds crystallize in the orthorhombic system with the following unit cell parameters: ErLiFe₂O₅, a = 10.510 Å, b = 10.776 Å, c = 14.270 Å, V ⁰ = 1616.16 ų; Z = 16, V _subcell ⁰ = 101.01 ų, ρ_X = 6.01 g/cm³, ρ_pycn = 5.97 ± 0.05 g/cm³; ErNaFe₂O₅, a = 10.519 Å, b = 10.785 Å, c = 15.510 Å, V ⁰ = 1759.56 ų, Z = 16, V _subcell ⁰ = 109.90 ų, ρ_X = 5.77 g/cm³, ρ_pycn = 5.72 ± 0.08 g/cm³; ErKFe₂O₅, a = 10.050 Å, b = 11.320 Å, c = 15.480 Å, V ⁰ = 1937.33 ų, Z = 16, V _subcell ⁰ = 121.08 ų, ρ_X = 5.46 g/cm³, ρ_pycn = 5.41 ± 0.04 g/cm³.     

Syntheses and Crystal Structures of Novel Ternary Alkali Metal Gold Acetylides MIAuC2 (MI = Li,Na, K,Rb, Cs)

By the reaction of AuI with alkali metal hydrogen acetylides M^IC₂H (M^I = Li–Cs) in liquid ammonia and subsequent heating of the remaining residue in refluxing pyridine (M^I = Li, Na, K) or as a solid phase at about 110 °C in vacuum (M^I = Rb, Cs) ternary alkali metal gold acetylides M^IAuC₂ were obtained. Their crystal structures were investigated by the means of X‐ray powder diffraction. [Au(C₂)_2/2^–] chains are the characteristic structural motif which are packed in a hexagonal (LiAgC₂) and tetragonal arrangement (NaAuC₂–CsAuC₂), respectively. Simple calculations based on the close packing of rods and spheres can explain these different arrangements. The existence of C–C triple bonds in the title compounds is confirmed by Raman spectroscopic investigations.     

Synthesis,characterization and self-assembly of amphiphilic block copolymer poly(4-vinyl benzene chloride)-b-poly(N-vinylpyrrolidone) in aqueous solution

The synthesis, characterization and self-assembly of a novel amphiphilic block copolymer containing a poly(N-vinylpyrrolidone) as a segment of hydrophilic and poly(4-vinyl benzene chloride) (PVBC) arms are reported. The copolymer was characterized by FT-IR spectroscopy ¹H NMR. The composition and the molecular weights of the block copolymers were established using gel permeation chromatography and ¹H NMR. The water-soluble fraction of poly(N-vinyl-2-pyrrolidone) (PVP)/PVBC block copolymers formed micelles which were investigated at 25 °C in water at 5 mg/ml concentration using a tensiometer. The morphology of micelles in aqueous solution was determined by the AFM, SANS, and SAXS methods.     

Chromites YbMCr<Subscript>2</Subscript>O<Subscript>5</Subscript> (M = Li,Na, K,Cs): X-ray diffraction study

Ytterbium alkali-metal chromites YbMCr₂O₅ (M = Li, Na, K, Cs) were synthesized by a ceramic procedure from the corresponding oxides and carbonates. Their crystal systems and unit cell parameters were determined by the homology method: for YbLiCr₂O₅, a = 10.34 Å, b = 10.62 Å, c = 15.05 Å, Z = 16, V ^o = 1653.74 ų, ρ_X-ray = 5.85 g/cm³, ρ_pycn = 5.81 ± 0.03 g/cm³; for YbNaCr₂O₅, a = 10.30 Å, b = 10.56 Å, c = 16.46 Å, Z = 16, V ^o = 1790.32 ų, ρ_X-ray = 5.64 g/cm³, ρ_pycn = 5.59 ± 0.07 g/cm³; for YbKCr₂O₅, a = 10.33 Å, b = 10.63 Å, c = 19.93 Å, Z = 16, V ^o = 2188.47 ų, ρ_X-ray = 5.95 g/cm³, ρ_pycn = 5.91 ± 0.03 g/cm³; and for YbCsCr₂O₅, a = 10.34 Å, b = 10.63 Å, c = 18.43 Å, Z = 16, V ^o = 2025.72 ų, ρ_X-ray = 5.19 g/cm³, ρ_pycn = 5.16 ± 0.05 g/cm³.     

Preparation,thermal property,and thermal stability of microencapsulated n-octadecane with poly(stearyl methacrylate) as shell

This study focused on preparation and thermal properties of poly(stearyl methacrylate) shell (PSMA) microcapsules containing n-octadecane as a phase change material (PCM). Pentaerythritol triacrylate (PETA) and divinylbenzene (DVB) were employed as crosslinking agents. The surface morphologies, particle sizes, and distributions of the microencapsulated phase change material (microPCM) were studied by scanning electron microscopy. The thermal properties, thermal reliabilities, and thermal stabilities of the microPCMs were investigated by differential scanning calorimetry and thermal gravimetric analysis. The microPCM with DVB exhibits higher phase change enthalpies of melting (87.9 J g^?1) and crystallization (94.8 J g^?1) and a greater thermal stability in comparison with the microPCM with PETA. The phase change temperatures and enthalpies of the microPCMs varied little after thermal cycles. Thermal images showed that the gypsum board with PSMA/n-octadecane microPCM possessed temperature-regulated property. Therefore, microencapsulated n-octadecane with PSMA as shell has good thermal energy storage and thermal regulation potential.     

Synthesis of poly(p-dioxanone)-based block copolymers in supercritical carbon dioxide

Poly(p-dioxanone)–poly(ethylene glycol)–poly(p-dioxanone) triblock copolymers (PPDO–PEG–PPDO) were first synthesized by suspension ring-opening polymerization (ROP) of p-dioxanone (PDO) in supercritical carbon dioxide (scCO₂) using different molecular weights (2–10 K) of poly(ethylene glycol) (PEG) as macroinitiators. White and fine flow powders were successfully obtained when the molecular weight of PEG was below 6 K and its feed content below 20 wt.%. The ¹H nuclear magnetic resonance (NMR) result indicated the formation of PPDO–PEG–PPDO block structure even in a confined polymerized environment of particles. All the powderous samples contained irregular shaped particles that were observed by scanning electron microscope (SEM). Except for the copolymer with 10 wt.% PEG10K feed content, the mean particle sizes of other powderous samples showed identical values close to 15 μm. This fact was in agreement with the crystallinity of PPDO in the copolymers measured by differential scanning calorimetry (DSC). The water absorption of these copolymers was also measured, and as compared with PPDO homopolymer, the introduction of PEG increased the water absorption of the copolymers. The green and environmentally friendly method disclosed in this work is attractive to directly synthesize biodegradable polymeric particles with potential biomedical applications.     

The crystal structures of α,ω-diaminoalkanecadmium(II) tetracyanonickelate(II)-aromatic molecule inclusion compounds. IV. (1,6-Diaminohexane)cadmium(II) tetracyanonickelate(II)-m-toluidine(1/1),-p-toluidine(1/1), and-2,4-xylidine(1/1) clathrates,and the coordination complex bis(p-toluidine) (1,6-diaminohexane)cadmium(II) tetracyanonickelate(II)

The crystal structures of the four title compounds have been analyzed by single crystal X-ray diffraction methods at room temperature. Three with a general formula Cd[NH₂(CH₂)₆NH₂]Ni(CN)₄·G (G=m-toluidine,Im;p-toluidine,Ip; and 2,4-xylidine,Ix) are the inclusion compounds of the respective aromatic molecules in the three-dimensional metal complex host (1,6-diaminohexane)cadmium(II) tetracyanonickelate(II). The remaining one is a coordination complex ofp-toluidine, bis(p-toluidine) (1,6-diaminohexane)cadmium(II) tetracyanonick-elate(II),II, Im, Ix, andII crystallize under similar experimental conditions;Ip is obtained using thep-toluidinemesitylene mixture at higher dilution than that used forII. Im crystallizes in the tri linic space group \(P\bar 1\) , witha=9.725(2),b=7.598(1),c=7.177(1) Å, α=90.44(1), β=98.80(1), γ=95.70(1)^o, andZ=1 (the final conventionalR=0.037 for 3526 reflections);Ip: monoclinic,P2/m,a=9.540(2),b=7.611(1),c=7.120(1) Å, β=100.95(1)^o, andZ=1 (R=0.027 for 1700 reflections);Ix: monoclinic,P2/m,a=9.628(2),b=7.613(1),c=7.122(1) Å, β=100.01(1)^o, andZ=1 (R=0.049 for 2704 reflections);II: monoclinic,P2₁/n,a=12.107(3),b=10.117(2),c=12.471(3) Å, β=113.67(2)^o, andZ=2 (R=0.037 for 2616 reflections). The structures ofIm, Ip andIx are similar to that of theo-toluidine inclusion compound of the same metal complex host. InII atrans pair of thep-toluidine molecules to the cadmium atom in the two-dimensional network formed by thecatena-μ-linkages of ?Cd?NH₂(CH₂)₆NH₂?Cd? and ?NC?Ni?CN?Cd?NC?Ni?CN?intersecting at each Cd atom; two cyanide groups of the tetracyanonickelate(II) moiety have free N-ends.     

Toward mechanized peptide synthesis via polymeric reagents approach

Simultaneous application of high-molecular-weight active esters and polyvinylN,N- diethylbenzylamine was used as a basis for a continuous peptide synthesis via the polymeric reagents approach. Using the synthetic procedure developed, the hexapeptide Boc-L-Pro-L-Val-L-Lys[Z(p-NO₂)]-L-Val-L-Tyr(Dnp)-L-Pro-OBzr¹ and the tetrapeptide Boc-l-Lys[Z(p-NO₂)]-L-Lys[Z(p-NO₂)]-L-Arg(NO₂)-L-Arg(NO₂)-OBzr, corresponding to residues 19–24 and 15–18 of human ACTH, were synthesized in 63 and 70% overall yields, respectively.