Über die quasi-binären Systeme NaNO2/Na2O und NaCN/Na2O. Phasendiagramme und Natrium-Ionenleitung in Na3O(NO2) und Na3O(CN)

On the Quasi-Binary Systems NaNO₂/Na₂O and NaCN/Na₂O. Phase Diagrams and Sodium Ion Conductivity of Na₃O(NO₂) and Na₃O(CN) Measurements of the electrical conductivities of Na₃O(NO₂) and Na₃O(CN) show sharp increases in conductivity at temperatures between 200° and 250°C, According to the phase diagrams of the quasi-binary systems NaNO₂/Na₂O and NaCN/Na₂O this is not an effect established by fusion. It seems to be a consequence of a “melting” of the sodium sublattice or the rotational disorder of complex anions.     

Laser-induced-fluorescence study of A Na/Na2 free jet. II. State-dependent effective inelastic cross sections for rotational and vibrational relaxation

Laser-induced-fluorescence measurements along the jet axis are used to study the relaxation of Na₂ molecules in a Na/Na₂ expansion. From the fluorescence intensity, the evolution of the occupancies of several vibration—rotation levels of the Na₂ ground state is obtained. The whole relevant region along the jet axis is covered: from the equilibrium region close to the nozzle down to the downstream part of the jet, where the internal-state distribution is non-Boltzmann and “frozen”. The relaxation of Na₂ molecules is analysed using first-order relaxation equations. Vibrational and rotational relaxation are treated separately by means of similar equations but with different inelastic cross sections determining the relaxation rates. The evolution of the vibrational levels can be described by means of a single effective cross section of = 100 Ų; the rotational cross sections are strongly J-state dependent and range from = 250 to 15 Ų, for J = 13-55.     

Analysis of Pure Rotational and Vibration‐rotational Spectra of NaCl X 1Σ+ and Quantum‐chemical Calculation of Related Molecular Properties

We fitted published frequency and wave number data for pure rotational and vibration‐rotational spectra, respectively, of ²³Na³⁵Cl and ²³Na³⁷Cl to derive parameters related to potential energy and to the rotational g factor. For comparison with these experimental data we undertook quantum‐chemical computation of adiabatic corrections, rotational and vibrational g factors, electric dipolar moment and its derivative as a function of internuclear distance in a range near R_e as a test of an algebraic approach to spectral analysis; experimental, 0.0287 ± 0.0014, and calculated, 0.02149, values of g_r at R_e are in moderate agreement. The combined results are discussed from a point of view of computational spectrometry.     

Long-range interactions in molecules and rotational coupling

We report a case study on Na₂ of the influence of rotational coupling for molecular states directly below the dissociation limit, where the electronic binding energy and the hyperfine interactions are of similar magnitude and the rotational energy can be varied from small to large compared to the former energies. The experimental observation and the theoretical analysis are important for obtaining precise data concerning long-range interactions and extrapolation to the dissociation limit, which are required for describing cold collisions in atomic traps. A consistent model for all observations with rotational quantum number J′ up to 41 is developed which involves few atomic parameters and demonstrates that these are sufficient to describe molecular levels few μeV below the dissociation energy.     

Laser Diagnostics of surface-emitted Na2 molecules

We report investigation on Na₂ molecules emitted from a liquid sodium surface into a vacuum. Vibrational and rotational temperatures of the emitted molecules agree with the temperature of the sodium surface, and the angular momenta of the emitted molecules are isotropically distributed. The experiments demonstrate an application of laser diagnostics for studies of a gas-liquid interface.     

Collision-induced rotational transitions in nali(1Π)

Collision-induced rotational transitions in the electronically excited NaLi molecule have been studied using laser excited fluorescence. Due to the greater number of allowed transitions as compared with Na₂ and Li₂, more cases were found of transitions +ΔJ and ?ΔJ having greatly different cross sections (“+/ - asymmetry”). This observation is in agreement with recent predictions on the basis of Born's approximation. All observed transitions are classified according to the symmetry of the contributing potential terms. Data are presented which indicate the necessity for refinements of the theory.     

Phase relations in the systems Na2OIrO2 and Na2OPtO2 in air

The equilibrium phase relations for the Na₂OIrO₂ and Na₂OPtO₂ systems were determined in air using the quenching technique. The Na₂OIrO₂ system contains two stable compounds Na₂O·IrO₂ and 2Na₂O·3IrO₂, which dissociate at 1235 and 1040°C, respectively. The Na₂OPtO₂ system contains three compounds: Na₂O·PtO₂, metastable 2Na₂O·3PtO₂, and Na_xPt₃O₄ (0 ? x ? 1). Their dissociation temperatures are 890, 710, and 810°C, respectively. Indexed X-ray diffraction powder patterns for Na₂O·IrO₂ and 2Na₂O·3IrO₂ are given.     

Experimental determination of the mj distribution in inelastic scattering of Na2 by He

The orientational distribution of Na₂ molecules scatterd by He has been determined in a molecules beam experiment. At large angle scattering where inelastic collisions are dominant, a high degree of alignment has been observed. This alignment depends strongly on the rotational quantum number J after scattering. The J dependence can be explained by assuming that during collisions m_j is conserved when the quantization axis is chosen parallel with the geometric apse.     

Systematic study of (Na n )2 dimer transient state in Na n +Na n collisions (n=8, 9, 19, and 20)

From distance dependent tight-binding molecular dynamics simulations, we systematically study the Na _n +Na _n collision dynamics around the first two closed shells (n=8 and 20). We investigate the stability of sodium cluster dimers (Na _n )₂, for many events with random relative orientation at finite temperature, various impact parameters and incident energies. We find that (Na₈)₂, (Na₉)₂, (Na₁₉)₂ and (Na₂₀)₂ can exist during about 3000 fs in central collisions while they can exist up to about ten thousands fs in peripheral collisions with larger impact parameters in fusion mechanism at c.o.m energy per atomE _cm/n=0.025 eV. We observe that the lower the incident energy, the longer the lifetime of the cluster dimers in both central and peripheral collisions. There is no apparent difference in the dynamical stability of (Na₈)₂ and (Na₉)₂, (Na₁₉)₂ and (Na₂₀)₂ although (Na₈)₂ and (Na₂₀)₂ are respectively slightly colder than (Na₉)₂ and (Na₁₉)₂ for the same incident energy per atom and the same impact parameter.     

On m-changes in atom-rigid-rotor collissions: influence of an initial rotation

Reorientation of the angular momentum of a diatomic molecule in collisions with atoms is investigated using classical mechanics. A factorisation formula for cross sections for rotational excitation is given. The factorisation allows the calculation of the state-specific cross section d σ (j′ m′ ← jm)/dΩ once the m-averaged cross sections d σ (j″← 0 )/dΩ for all possible j″ are known. The approach is applied to the Na₂-He system.     

Solid phase reactivity of sodium oxosalts of manganese

The observed relationships are presented of the solid phase reactivity of the following salts: NaMnO₄, Na₂MnO₄, Na₃MnO₄, Na₄MnO₄, Na₂MnO₃, Na₂Mn₂O₅, Na₅MnO₄, Na₄Mn₂O₅, NaMnO₂, Na₄MnO₃, Na₂MnO₂ and Na₂Mn₂O₃.     

Quasi-resonant energy transfer in collisions: Na2(A1Σ u + )+K(4S)

Cross sections for electron energy transfer from the initial rotational stateJ′of the two lowest vibrational levelsv′=0 andv′=1 of excited dimers Na₂(A) to potassium atoms as described by Na₂(A¹Σ _u ⁺ ,v′J′)+K(4S)→Na₂ (X¹Σ _g ⁺ ,v″J″)+K(4P)+ΔE have been examined by laser-induced fluorescence. A strong increase of the cross section by as much as an order of magnitude has been observed for those dimerv′J′-levels for which the dipole transitions are close to resonance of the 4S-4P transitions in the atom (ΔE<4 cm^?1). The absolute cross sections for energy transfer have been calculated by the Rabitz approximation of first-order perturbation theory. In the case of closest energy resonance (ΔE=0.9 cm^?1) the cross section is Q=7.8×10^?13 cm².     

Darstellung und Kristallstruktur der Pnictidoxide Na2Ti2As2O und Na2Ti2Sb2O

Preparation and Crystal Structure of the Pnictide Oxides Na₂Ti₂As₂O and Na₂Ti₂Sb₂O Na₂Ti₂As₂O and Na₂Ti₂Sb₂O were synthesized in form of very easily hydrolysed metallic-grey powders by reaction of Na₂O and TiAs resp. TiSb in sealed tantalum tubes under argon. The tetrahedral bodycentered crystallizing compounds from a modified anti-K₂NiF₄ structure type [1] (also called Eu₄As₂O-type [2,3]), space group I4/mmm (no. 139), with the lattice constants for Na₂Ti₂As₂O: a = 407.0(2) pm, c = 1528.8(4) pm and for Na₂Ti₂Sb₂O: a = 414.4(0) pm, c = 1656.1(1) pm. Magnetic measurements of powder samples of Na₂Ti₂Sb₂O show antiferromagnetic interaction within the Ti—O-layers. Superconductivity was not found by ac-shielding method down to 4 K.     

Theoretical investigation of the Na+ + H2 system. III. Trajectory calculations of vibrationally inelastic collision processes

On the basis of an analytical potential energy surface for the electronic ground state of the Na⁺ + H₂ system reported recently, extensive trajectory calculations have been performed to study the collision dynamics of vibrationally inelastic processes at total energies up to ～3 eV. Special attention is given to the relative efficiacy of translational and rotational energy, respectively, in promoting vibrational energy transfer. Vibrational transitions are found to be substantially enhanced by initial molecular rotation. Furthermore, the applicability of simple models is discussed.     

Fundamentals in CO_2 capture of Na_2CO_3 under a moist condition

Capacity and kinetics of CO_2 capture of Na_2CO_3 were studied to determine the mechanism for CO_2 sequestration under ambient conditions. Bicarbonate formation of Na_2CO_3 was examined by a thermogravimetric analysis(TGA) under various CO_2 and water vapor concentrations and the accompanying structural changes of Na_2CO_3 were demonstrated by X-ray diffraction(XRD). Morphological variations were observed during the reaction of CO_2 capture through scanning electron microscope(SEM). Structural changes and morphological variations, which occurred during the course of the reaction, were then connected to the kinetic and exothermic properties of the CO_2 capture process from the XRD and SEM measurements. The results showed that the bicarbonate formation of Na_2CO_3 has two different pathways.For higher CO_2 and H_2O concentrations, the bicarbonate formation proceeded effectively. However, for lower CO_2 and H_2O concentrations, the reactions were more complicated. The formation of Na_2CO_3·H_2O from Na_2CO_3 as the first step, followed by the subsequent formation of Na_5H_3(CO_3)_4, and then the bicarbonate formation proceeds. To understand such fundamental properties in CO_2 capture of Na_2CO_3 is very important for utilization of Na_2CO_3 as a sorbent for CO_2 capture.     

Phasenbeziehungen und Natriumionenleitung im quasi-binären System Na2SiF6/Na3AlF6

Phase Relations and Sodium Ion Conductivity within the Quasi-binary System Na₂SiF₆/Na₂AIF₆ . The phase diagram of the Na₂SiF₆/Na₃AlF₆ system has been determined by means of x-ray powder diffraction, thermal analysis and conductivity measurements in the sub-solidus region. Na₃AlF₆ accomodates up to 73 mol.-% Na₂SiF₆ maintaining the crystal structure type. The sodium ion conductivity increases by about five orders of magnitude upon doping Na₃AlF₆ with Na₂SiF₆.     

Über Na2PrO3 und Na2TbO3

On Na₂PrO₃ and Na₂TbO₃ Using an exchange reaction of Na₂O with Li₈TbO₆ (Na : Tb = 2.1 : 1; au-tube; 750°C, 30 d) yellow-orange colored single crystals of Na₂TbO₃ could be prepared for the first time. Na₂TbO₃ crystallizes monoclinic in C2/c (Z = 8; a = 576.92(6), b = 1001.27(9), c = 1117.91(14) pm, β = 99.98(1)°). According to four-circle data the Li₂SnO₃-type of structure is adopted (PW 1100, MoKα , 1935 I₀ (hkl), R = 4.86%, R_w = 3.63% for all 928 unique reflexions). By a similar exchange reaction of Na₂O with Li₈PrO₆ for the first time single crystals of Na₂PrO₃ could be prepared, too (Na : Pr = 2.2 : 1; au-tube; 700°C; 23 d). The structure determination reveils that there is a variant of the NaCl-type of structure, which ressembles to the Li₂SnO₃-type of structure (PW 1100, MoKα , 2199 I₀ (hkl)), R = 8.88%, R_w = 5.21% for all 947 unique reflexions; C2/c, Z = 8, a = 678.78(5), b = 977.47(7), c = 1080.38(9) pm, β = 108,4(1)°. In contrast to Na₂TbO₃ there are no layers according to NaO(Na_1/3Tb_2/3)O. All octahedral intersticies are occupied systematically with Pr⁴⁺ and Na⁺ : (Na_2/3Pr_1/3)O(Na_2/3Pr_1/3)O.     

Einbau von Na2SO4 in die Hochtemperaturform des Na3PO4

Formation of Solid Solutions of Na₂SO₄ in the High-temperature Form of Na₃PO₄ The high-temperature form of Na₃PO₄ solves up to 70 mole-% Na₂SO₄ maintaining the type of crystal structure. The lattice constants increase from 742.3(1) pm (pure Na₃PO₄) to 749.1(2) pm for Na^3?x(PO₄)^?x(SO₄)_x (x = 0.7). The high-temperature form, in the case of pure Na₃PO₄ stable above 325°C, is stabilized at room-temperature by doping with small amounts of Na₂SO₄.     

Spray-drying as a tool to disperse conductive carbon inside Na<Subscript>2</Subscript>FePO<Subscript>4</Subscript>F particles by addition of carbon black or carbon nanotubes to the precursor solution

In this work, Na₂FePO₄F-carbon composite powders were prepared by spray-drying a solution of inorganic precursors with 10 and 20 wt% added carbon black (CB) or carbon nanotubes (CNTs). In order to compare the effect of CB and CNT when added to the precursor solutions, the structural, electrochemical, and morphological properties of the synthesized Na₂FePO₄F-xCB and Na₂FePO₄F-xCNT samples were systematically investigated. In both cases, X-ray diffraction shows that calcination at 600 °C in argon leads to the formation of Na₂FePO₄F as the major inorganic phase. ⁵⁷Fe Mössbauer spectroscopy was used as complementary technique to probe the oxidation states, local environment, and identify the composition of the iron-containing phases. The electrochemical performance is markedly better in the case of Na₂FePO₄F-CNT (20 wt%), with specific capacities of about 100 mAh/g (Na₂FePO₄F-CNT) at C/4 rate vs. 50 mAh/g for Na₂FePO₄F-CB (20 wt%). SEM characterization of Na₂FePO₄F-CB particles revealed different particle morphologies for the Na₂FePO₄F-CNT and Na₂FePO₄F-CB powders. The carbon-poor surface observed for Na₂FePO₄F-CB could be due to a slow diffusion of carbon in the droplets during drying. On the contrary, Na₂FePO₄F-CNT shows a better CNT dispersion inside and at the surface of the NFPF particles that improves the electrochemical performance.     

Stages of thermal decomposition of sodium oxo-salts of sulphur

Thermal behaviour of sodium oxo-salts of sulphur: Na₂SO₄, Na₂S₂O₇, Na₂S₂O₆, Na₂SO₃, Na₂S₂O₅, Na₂S₂O₄, Na₂S₂O₃, Na₂S₃O₆ and of sulphides Na₂S and Na₂S₂ was studied on heating up to 1000°C. The experiments were performed with anhydrous compounds obtained from commercial products by recrystallisation and dehydration. The stage mechanisms of decomposition of anionic sub-lattices of the salts have been proposed basing on the Górski’s morphological classification of simple species. The thermal stability and the stage decomposition mechanisms were correlated with the structure and the potential chemical properties of the salt anions. The thermal decomposition processes were studied by means of thermal analysis, and the decomposition products were identified by means of X-ray phase analysis.