Cold collisions of N (4S) atoms and NH (3Σ) molecules in magnetic fields

We calculate the interaction potential between N atoms and NH molecules and use it to investigate cold and ultracold collisions important for sympathetic cooling. The ratio of elastic to inelastic cross sections is large over a wide range of collision energy and magnetic field for most isotopic combinations, so that sympathetic cooling of NH molecules by N atoms is a good prospect. However, there are important effects due to a p-wave shape resonance that may inhibit cooling in some cases. We show that scaling the reduced mass used in the collision is approximately equivalent to scaling the interaction potential. We then explore the dependence of the scattering properties on the reduced mass and explain the resonant effects observed using angular-momentum-insensitive quantum defect theory.     

Structures and defects of Au particles (1–3 nm) by HREM

Gold particles produced by the inert gas aggregation technique were observed in HREM. Among the smallest ones (1–3 nm), four structures were recognized: decahedra, icosahedra, cuboctahedra and body-centered tetragonal or orthorhombic structures. The observation of the latter structure for Au clusters is reported for the first time. By improved image processing, their morphologies and defects were precisely determined. Most of them contained small distortions compared to the ideal structures.     

Experimental verification of strong rotational dependence of fluorescence and predissociation yield in the b1Πu(v = 1) level of 14N2

New, rotationally resolved fluorescence-excitation spectra confirm coupled-channel Schro?dinger-equation predictions of strong rotational dependence of the fluorescence and predissociation yields in the b(v = 1) level of (14)N(2).     

Investigating the local structure of B-site cations in (1-x)BaTiO3–xBiScO3 and (1-x)PbTiO3–xBiScO3 using X-ray absorption spectroscopy

The structural properties of (1-x)BaTiO₃–xBiScO₃ and (1-x)PbTiO₃–xBiScO₃ were investigated using powder X-ray diffraction and X-ray absorption spectroscopy. Diffraction measurements confirmed that substituting small amounts of BiScO₃ into BaTiO₃ initially stabilizes a cubic phase at x = 0.2 before impurity phases begin to form at x = 0.5. BiScO₃ substitution also resulted in noticeable changes in the local coordination environment of Ti⁴⁺. X-ray absorption near-edge spectroscopy (XANES) analysis showed that replacing Ti⁴⁺ with Sc³⁺ results in an increase in the off-centre displacement of Ti⁴⁺ cations. Surprisingly, BiScO₃ substitution has no effect on the displacement of the Ti⁴⁺ cation in the (1-x)PbTiO₃–xBiScO₃ solid solution.     

Modulating opto-electronic and magnetic responses of Mo- and Zn-adsorbed LiNbO3 (1 1 1) surface for advanced energy harvesting applications: A comprehensive study

This study aimed to comprehensively investigate the optoelectronic and magnetic properties of Mo, Zn/LiNbO₃ (1 1 1) material. The primary objectives were to understand the potential for manipulating the material's magnetism and to elucidate the origin of spin-polarized states and magnetic moments, particularly with respect to the unpaired d orbitals of Nb, Mo, and Zn atoms. To achieve these objectives, we employed the Pardew–Burke–Ernzerhof (PBE) method within the Generalized Gradient Approximation (GGA + U) framework. This computational approach allowed us to examine the optoelectronic and magnetic characteristics of the material in detail. Our research yielded several key findings that enhance our understanding of Mo, Zn/LiNbO₃ (1 1 1) material. We observed a modest improvement in the material's absorption capacity within the visible spectrum, accompanied by a discernible red-shift. Notably, our study involved the calculation of the dielectric function and refractive constant of the material, revealing a strong correlation between absorption trends and the dielectric constant. Furthermore, our investigation uncovered that Mo, Zn/LiNbO₃ (1 1 1) exhibits distinct conduction and valence bands, with p and d orbitals predominantly contributing to each, respectively. The energy gap of the material falls within a range of 0.30–1.04 eV. A particularly significant finding was the narrower band gap of Mo, Zn/LiNbO₃ (1 1 1) material, which can be attributed to the superposition of Mo-d and Zn-p orbit energy levels with O-p orbit energy levels, ultimately forming a covalent bond. Importantly, our research demonstrated the material's heightened optical absorption within the visible spectrum, suggesting its suitability for various photonic and optoelectronic applications. Additionally, we calculated a wide range of optical characteristics, including the dielectric function, absorption coefficient, energy loss, reflectivity, refractive index, extinction coefficient, and optical conductivity, providing a comprehensive assessment of the material's optical properties.     

Trifluoromethylation of [AuF3(SIMes)]: Preparation and Characterization of [Au(CF3)xF3−x(SIMes)] (x=1–3) Complexes

Trifluoromethylation of [AuF₃(SIMes)] with the Ruppert–Prakash reagent TMSCF₃ in the presence of CsF yields the product series [Au(CF₃)_xF_3−x(SIMes)] (x=1–3). The degree of trifluoromethylation is solvent dependent and the ratio of the species can be controlled by varying the stoichiometry of the reaction, as evidenced from the ¹⁹F NMR spectra of the corresponding reaction mixtures. The molecular structures in the solid state of trans-[Au(CF₃)F₂(SIMes)] and [Au(CF₃)₃(SIMes)] are presented, together with a selective route for the synthesis of the latter complex. Correlation of the calculated SIMes affinity with the carbene carbon chemical shift in the ¹³C NMR spectrum reveals that trans-[Au(CF₃)F₂(SIMes)] and [Au(CF₃)₃(SIMes)] nicely follow the trend in Lewis acidities of related organo gold(III) complexes. Furthermore, a new correlation between the Au−C_carbene bond length of the molecular structure in the solid state and the chemical shift of the carbene carbon in the ¹³C NMR spectrum is presented.     

First-principles calculations on the structures,magnetic, and electronic properties of the (Fe2N)m (m = 1–4) and (Fe3N)n (n = 1–3) clusters

The structures, magnetic, and electronic properties of the ground-state (Fe₂N)_m (m?=?1–4) and (Fe₃N)_n (n?=?1–3) clusters have been investigated by using first-principles. The structure of the (Fe₂N)_m and (Fe₃N)_n clusters is a compromise that the N atoms approach more Fe atoms and the N atoms repel each other. The structural stabilities of the (Fe₂N)_m and (Fe₃N)_n clusters increase with the increasing of the N ratio except for the Fe₆N₃ clusters. The (Fe₂N)_m (m?=?1–4) and Fe₉N₃ clusters exhibit more kinetic stabilities than pure iron clusters. The N substitution can decrease the average spin densities of small iron clusters except for the Fe₆N₂ and Fe₈N₄ clusters. The Fe–N bonds exhibit certain covalent bond characteristics.

     

Application of high-field proton nuclear magnetic resonance (1H-NMR) spectroscopy for the analysis of explosives and related compounds in groundwater samples – a comparison with the high-performance liquid chromatography (HPLC) method

High-field proton nuclear magnetic resonance (¹H-NMR) spectroscopy was applied to the analysis of nitroaromatics and nitramines in ammunition waste water. The ¹H-chemical shifts data of a variety of reference compounds are presented. Three groundwater samples, taken near the former ammunition plant Elsnig (Saxony), were analysed by high-performance liquid chromatography (HPLC) and by proton nuclear magnetic resonance spectroscopy. The results of HPLC and NMR analyses are compared and discussed.     

Structural, electronic, bonding, magnetic, and optical properties of bimetallic [Ru(n)Au(m)](0/+) (n + m ≤ 3) clusters

The structural, electronic, bonding, magnetic, and optical properties of bimetallic [Ru(n)Au(m)](0/+) (n + m ≤ 3; n, m = 0-3) clusters were computed in the framework of the density functional theory (DFT) and time-dependent DFT (TD-DFT) using the full-range PBE0 non local hybrid GGA functional combined with the Def2-QZVPP basis sets. Several low-lying states have been investigated and the stability of the ground state spinomers was estimated with respect to all possible fragmentation schemes. Molecular orbital and population analysis schemes along with computed electronic parameters illustrated the details of the bonding mechanisms in the [Ru(n)Au(m)](0/+) clusters. The TD-DFT computed UV-visible absorption spectra of the bimetallic clusters have been fully analyzed and compared to those of pure gold and ruthenium clusters. Assignments of all principal electronic transitions are given and interpreted in terms of contribution from specific molecular orbital excitations.     

Quasi-classical trajectory-gaussian binning study of the OH + D2 → HOD(v1',v2',v3') + D angle-velocity and vibrational distributions at a collision energy of 0.28 eV

The angle-velocity and product vibrational state distributions for the OH + D(2) reaction at a collision energy of 0.28 eV have been calculated using the quasi-classical trajectory-gaussian binning (QCT-GB) method and the Wu-Schatz-Lendvay-Fang-Harding (WSLFH) analytical potential energy surface. Comparison with high resolution molecular beam experiments shows that, differing from what happens when using the standard QCT method (i.e., histogram binning), very good results are obtained for both distributions. Hence, the strong differences previously observed between QCT and experimental results mainly come from an inadequate pseudoquantization of HOD rather than from other quantum effects. This is probably the first time that such a high level of agreement between theory and high resolution experimental data has been found in polyatomic reaction dynamics.     

Coherence and correlation parameters for thed 3 Π u − (v=0,1,2,3;N=1) states of H2

We have applied the density matrix formalism and the distorted-wave approximation to calculate the Stokes parameters for thed ³ Π _u ^? (v=0,1,2,3;N=1) states of H₂ excited from the X¹ ∑ _g ⁺ (v=0,N=1) state by electron impact at the incident energies ranging from 15 to 40 eV. Our results show that these parameters are nearly independent of the vibrational quantum number of the excited states. However, the polarization of the radiation emitted by the target in the subsequent decay process increases with increasing incident energies.     

Structure, IR and Mössbauer spectra, and magnetic properties of [Fe2CoO(CH3COO)6(3-CI-Py)3]· 1/4· 3-Cl-Py· 1/4(CH3)2CO· 1/2H2O

The structure of the hetemnuclear iron acetate [Fe₂CoO(CH₃COO)₆(3-Cl-Py)₃]·1/4· 3-Cl-y× 1/4(CH₃)₂CO· 1/2H₂O was determined by X-ray structure analysis. The crystal has a molecular structure and is monoclinic with lattice parameters a = 21.034(4). b = 8.398(2), c = 23.360(5) Å, β= 98.28(3)?, R = 0.0656. space group P2₁/c. The trinuclear complex [Fe₂CoO(CH₃COO)₆(H₂O)₃] has a structure typical for iron(III) μ₃-O compounds with iron atoms hing at the vertices of the equilateral triangle centered by an oxygen atom. The metal atoms are each coordinated to four oxygen atoms of the four bridging carboxy groups, the bridging oxygen atom (μ₃-O), and the coordinated 3-chloropyridine molecule which is trans relative to the latter atom. According to Mössbauer spectroscopy data, the iron(III) ions are in the high-spin state. The value of (μ_ef)_mole/μ₃ at room temperature and its temperature dependence suggest that the resulting magnetic exchange interaction between the paramagnetic centers of the cluster is antiferromagnetic.     

The reaction of [W(PMe3)4(η2-CH2PMe2)H] with carbon dioxide and dihydrogen: characterisation of [{W(PMe3)3(η1-PMe2CH2)}2(C3H2O6)] using two-dimensional nuclear magnetic resonance spectroscopy

[W(PMe₃)₄(η²-CH₂PMe₂)H] reacts with a mixture of CO₂ and H₂ (1/1, 3 atm) at room temperature to give [W(PMe₃)₄H₂(η²-O₂CO)] and [{W(PMe₃)₃(η¹-PMe₂CH₂)}₂(C₃H₂O₆)]. [{W(PMe₃)₃(η¹-PMe₂CH₂)}₂(C₃H₂O₆)] has been characterised using two-dimensional homo- and hetero-nuclear correlation NMR techniques.     

Nature of conductivity of Perovskites La1 ? x Sr x ScO3 ? α (x = 0.01–0.15) under oxidative and reducing conditions

Transport numbers of ions and protons are measured on ceramic samples of La_{1 ? x} Sr _x ScO_{3 ? ??} (x = 0.01?C0.15); partial conductivities (hole, proton, and oxygen-ion) are determined in the temperature range of 500?C900°C at pH₂O = 0.04?C2.35 kPa and pO₂ from air to 10^?15 Pa.     

Spectroscopic and structural studies of quinoline derivatives—II. Forrier transform i.r. spectroscopy. 1. Rotational isomerism in 3-ethoxycarbonyl-4(1H)-quinolone and some of its substituted derivatives

Rotational isomerism associated with internal rotation about the ring carbon(3)-ester carbonyl carbon single bond in a series of 3-ethoxycarbonyl-4(1H)-quinolones have been investigated spectroscopically in the solid state using Fourier transform i.r. and laser Raman spectroscopy. Particular attention is given to the 1700, 1300 and 1100 cm⁻¹ spectral regions related primarily to the vibrations of the CO₂C₂H₅ group. Within these regions rotational isomerism appeared in the compounds examined. The conformational changes are discussed and evidence is reported for occurrence of the unsubstituted compound 1 itself in the solid state at ambient temperature as an equilibrium mixture of both the s-trans (1a) and s-cis (1b) rotamers (this is in contrast to previous findings), and of its Bz-substituted derivatives.     

Structural,electrochemical, electronic,and magnetic properties of monoclinic LixV2(PO4)3 for x = 3, 2, 1 using first-principles calculations

Journal of Solid State Electrochemistry - Monoclinic lithium vanadium phosphate Li3V2(PO4)3 is a very promising cathode candidate for applications in Li-ion batteries, with a high operational...     

Phase composition and conductivity of La1 ? x Sr x ScO3 ? α (x = 0.01?0.20) under oxidative conditions

The phase composition was studied and overall conductivity of oxides La_{1 ? x} Sr _x ScO_{3 ? ??} (x = 0.01?0.20) was measured as dependent on air humidity (pH₂O = 0.04?2.35 kPa) in the temperature range from 100 to 900°C. The samples were synthesized in air at 1600°C. They are single-phase, with a perovskitetype structure with orthorhombic distortions and the density of 94?C99%. The conductivity measurements were carried out using the impedance technique and four-probe dc technique. The contributions of bulk and grain boundary resistances were determined, effective conductivity activation energies were calculated.     

Structures,electronic and magnetic properties of the FemOn@Cx (m = 1–3, n = 1–4, x = 50, 60) clusters

The structures, electronic and magnetic properties of the Fe_mO_n@C_x (m?=?1–3, n?=?1–4, x?=?50, 60) clusters have been investigated by using PBE functional. The C₅₀, C₆₀ can significantly increase the structural stabilities of the Fe_mO_n molecules. Fe₂O₃@C₅₀ and Fe₃O₄@C₅₀ are more chemically stable than the Fe₂O₃@C₆₀ and Fe₃O₄@C₆₀ while FeO@C₆₀ is more chemically stable than the FeO@C₅₀. The spin densities of the Fe_mO_n fragments degenerate to zero. Carbon encapsulation leads to the internal charges of the Fe_mO_n fragments transfer from 4 s to 4p orbital.

     

How reliable are GIAO calculations of 1H and 13C NMR chemical shifts? A statistical analysis and empirical corrections at DFT (PBE/3z) level

Reliability of calculated (1)H and (13)C NMR chemical shifts for various classes of organic compounds obtained with gauge-invariant atomic orbital (GIAO) approach has been studied at the PBE/3ζ level (as implemented in PRIRODA code) using linear regression analysis with experimental data. Empirical corrections for the calculated chemical shifts δ(H,calc) = δ(PBE/3ζ) - 0.08 ppm (RMS 0.18 ppm, MAD 0.66 ppm) and δ(C,calc) = δ(PBE/) (3) (ζ) - 6.35 ppm (RMS 3.09 ppm, MAD 9.42 ppm) have been developed using the sets of 263 and 308 experimental values for (1)H and (13)C chemical shifts, respectively. The confidence intervals of NMR chemical shifts at 95% confidence probability are δ(H,calc) ± 0.35 ppm for (1)H and δC,calc) ± 6.05 ppm for (13)C.