Vibrational spectroscopic study of the mineral penkvilksite Na 2TiSi 4O 11·2H 2O – a mineral used for the uptake of radionuclides

We have used vibrational spectroscopy to study the formula and molecular structure of the mineral penkvilksite Na ₂TiSi ₄O ₁₁·2H ₂O. Penkvilksite is a mineral which may be used in the uptake of radioactive elements. Both Raman and infrared spectroscopies identify a band at ～3638 cm^?1 attributed to an OH-stretching vibration of hydroxyl units. The inference is that OH units are involved in the structure of penkvilksite. The formula may be well written as Na ₂TiSi ₄O ₁₀(OH)₂·H ₂O. The mineral is characterised by a very intense Raman band at 1085 cm^?1 and a broad infrared band at 1080 cm^?1 assigned to SiO-stretching vibrations. Raman bands at 620, 667 and 711 cm^?1 are attributed to SiO and TiO chain bonds. Water-stretching vibrations are observed as Raman bands at 3197, 3265, 3425 and 3565 cm^?1. Vibrational spectroscopy enables aspects of the molecular structure of the mineral penkvilksite to be ascertained. Penkvilksite is a mineral which can incorporate actinides and lanthanides from radioactive waste.     

Vibrational Kinetics of the Lüders Front

Russian Physics Journal - The regularities in the inhomogeneous development of plastic deformation at the front of the Lüders band at the yield plateau in Hadfield steel single crystals are...     

Formation and spectroscopic characterization of mono-dispersed CdSe nanocrystals

In this article, mono-dispersed hexagonal structure CdSe nanocrystals with polyhedron shape were prepared by an open solvent thermal reaction. They show a discrete excitonic transition structure in the absorption spectra and the minimal photoluminescence （PL） peak full-width at half-maximum of 19nm. The PL quantum yield is about 60%. Transmission electron micrographs, high-resolution transmission electron micrographs, x-ray powder diffraction patterns, UV-vis absorption spectra and PL spectra were obtained for the as-prepared CdSe nanocrystals. The size of the CdSe nanocrystals can be tuned by changing the reaction temperature or time. Due to the improved synthesis method, a different growth mechanism of the CdSe nanocrystals is discussed.     

Vibrational Analysis of the β System of 10B18O

Ten bands of the β system (B²Σ⁺ ? X²Σ⁺) of the ¹⁰B¹⁸O molecule have been observed for the first time. The spectrum was obtained by emission spectroscopy from a low‐pressure arc, at medium dispersion, and vibrationally analyzed using isotope shift measurements. Vibrational analysis gave the constants ω_e and ω_ex_e for both electronic states involved in the transitions.     

Non-equilibrium carbothermic reduction of magnesium at the treatment of agglomerated particles “magnesium oxide–carbon” in the plasma jet

Theoretical estimations are made in order to support the possibility of the non-equilibrium carbothermic reduction of magnesium after the plasma treatment of agglomerated particles-decamicron mechano-composites which consist of uniformly mixed reacting nano- and sub-micron insertions of magnesium oxide and soot with the preset stoichiometric composition. Experimental results are presented to confirm the practical attainability of the process.     

Vibrational Spectroscopy of the Borate Mineral Priceite—Implications for the Molecular Structure

ABSTRACT

Priceite is a calcium borate mineral and occurs as white crystals in the monoclinic pyramidal crystal system. We have used a combination of Raman spectroscopy with complimentary infrared spectroscopy and scanning electron microscopy with Energy-dispersive X-ray Spectroscopy (EDS) to study the mineral priceite. Chemical analysis shows a pure phase consisting of B and Ca only. Raman bands at 956, 974, 991, and 1019 cm^?1 are assigned to the BO stretching vibration of the B₁₀O₁₉ units. Raman bands at 1071, 1100, 1127, 1169, and 1211 cm^?1 are attributed to the BOH in-plane bending modes. The intense infrared band at 805 cm^?1 is assigned to the trigonal borate stretching modes. The Raman band at 674 cm^?1 together with bands at 689, 697, 736, and 602 cm^?1 are assigned to the trigonal and tetrahedral borate bending modes. Raman spectroscopy in the hydroxyl stretching region shows a series of bands with intense Raman band at 3555 cm^?1 with a distinct shoulder at 3568 cm^?1. Other bands in this spectral region are found at 3221, 3385, 3404, 3496, and 3510 cm^?1. All of these bands are assigned to water stretching vibrations. The observation of multiple bands supports the concept of water being in different molecular environments in the structure of priceite. The molecular structure of a natural priceite has been assessed using vibrational spectroscopy.     

An Overview of the High‐Pressure Vibrational Spectra of Clays and Related Minerals

Abstract

An overview of the effect of high external pressures on clays and related minerals is presented. The results show that this is an area that will welcome further investigation in the future, especially in view of the importance of clay minerals in the Earths's mantle and, possibly, even in prebiotic chemistry in the formation of amino acids and the mineralogy of the Martian surface.     

Invariants for the topological characterization of the iteration of differentiable functions – the bimodal case

We consider dynamical systems defined by a particular class of differentiable functions, as fixed state space. The dynamics is given by the iteration of an operator induced by a polynomial map which belongs to an appropriate family of isentropic bimodal interval maps. We characterize topologically these dynamical systems, in particular using the invariants defined for the iteration of the bimodal interval maps.     

Construction of the Structural Dynamic Model of β-Chlorovinyl Dichloroarsine and Analysis of Its Vibrational Spectrum

The possibility of using experimental and theoretical methods of optical physics to construct structural dynamic models of the lewisite (-chlorovinyl dichloroarsine) molecule in various media of interest for ecological monitoring is shown.     

Dielectronic recombination rates for ions of the magnesium sequence—II

The dielectronic recombination (DR) rate coefficient α^DR is explicitly calculated for Ar, Fe and Mo target ions of the Mg isoelectronic sequence (12 electrons). The 2p transitions are dominant at high temperatures and are considered in detail with full LS coupling. This work extends our previous study in which both the 3s, Δn = 0 and 3s, Δn ≠ 0 transitions are considered. Scaling of α^DR with free-electron temperature is also discussed.     

Features of the Percolation Scheme of Vibrational Spectrum Reconstruction in the Ga1 – xAl x P Alloy

Specific features of the properties of Ga–P lattice vibrations have been investigated using the percolation model of a mixed Ga_{1 – x}Al _x P crystal (alloy) with zero lattice mismatch between binary components of the alloy. In contrast to other two-mode alloy systems, in Ga_{1 – x}Al _x P a percolation splitting of δ ~ 13 cm^–1 is observed for the low-frequency mode of GaP-like vibrations. An additional GaP mode (one of the percolation doublet components) split from the fundamental mode is observed for the GaP-rich alloy, which coincides in frequency with the gap corresponding to the zero density of one-phonon states of the GaP crystal. The vibrational spectrum of impurity Al in the GaP crystal has been calculated using the theory of crystal lattice dynamics. Upon substitution of lighter Al for the Ga atom, the calculated spectrum includes, along with the local mode, a singularity near the gap with the zero density of phonon states of the GaP crystal, which coincides with the mode observed experimentally at a frequency of 378 cm^–1 in the Ga_{1 – x}Al _x P (x < 0.4) alloy.

     

Vibrational spectroscopic and DFT calculation studies of a new organic–inorganic compound of bis (4-acetylanilinium) tetrachlorocadmiate (II)

The FT-IR and Raman vibrational spectra of bis (4-acetylanilinium) tetrachlorocadmiate (II) compound have been measured at room temperature by FT-infrared spectroscopy (4000–400 cm⁻¹) on polycrystalline samples, and by Raman spectroscopy (3600–30 cm⁻¹) on monocrystals. The structure of the [C₈H₁₀NO] ₂CdCl₄ formed by two cations [C₈H₁₀NO]⁺ of same type and one type of anion [CdCl₄]²⁻ was optimized by density functional theory (DFT) using the B3LYP method. The theoretical wavenumbers spectra were scaled by multiple scaling factors, yielding a good agreement between the experimentally recorded and the theoretically calculated values. Root mean square (rms) value was calculated and the small difference between experimental and calculated modes has been interpreted by intermolecular interactions in the crystal. The comparison between the [C₈H₉NO] ligand and the [C₈H₁₀NO]₂[CdCl₄] compound of the Raman spectra showed a decrease in the wavenumber of the bands assigned to the stretching vibration of (NH₃) group in the compound due to the effect of the protonation of the nitrogen.     

A photoelectron spectroscopic study of the second ionisation of the CF(X2Π) radical

The CF(X²Π) radical has been re-investigated with vacuum ultraviolet photoelectron spectroscopy. Two bands were observed and assigned to the ionisations CF⁺(X¹Σ⁺)←CF(X²Π) and CF⁺(a³Π)← CF(X²Π). The first band, which has been observed previously, has an adiabatic ionisation energy of (9.11±0.02) eV and a vertical ionisation energy of (9.55±0.02) eV. For the second band, three vibrational components were observed with the first, the most intense, at an ionisation energy of (13.94±0.02) eV. Analysis of the vibrational structure in the two observed bands allowed ω_e and r_e to be determined as 1810±30 cm⁻¹ and 1.154±0.005 Å, respectively for the first ionic state, CF⁺(X¹Σ⁺), and 1614±30 cm⁻¹ and 1.213±0.005 Å, respectively for the second ionic state, CF⁺(a³Π). Comparison of the ionisation energies and spectroscopic constants obtained has been made with values obtained from recent multi-reference configuration interaction calculations.     

IR spectroscopic investigation of the structure of water–fuel microemulsion for diesel engines

The structures of a microemulsion formed by a surfactant (ammonium oleate), water drops of a linear size of 1–3 µm, and a diesel fuel has been investigated using IR spectroscopy. It has been found that ammonium oleate molecules in the microemulsion are dissociated on the positive NH₄⁺ ion and the negative ion of the remaining part of the molecule, which forms the hydrogen bond with water molecules. This increases the rate of water, evaporation and leads to the more complete combustion of the diesel fuel. As a result, the concentration of harmful nitrogen oxides and soot particles in the exhaust gas of the diesel engine decreases.     

Vibrational analysis of the (B 2 П→X 2 П) system of NS

A few red degraded bands attributable to NS have been reported earlier byFowler andBarker, Dressler andBarrow et al, and they occur in the same region (2300 to 2700 Å) as the bands of the known systems (C ² ∑ ⁺?X ² П) and (A ² Δ?X ² П). Measurements made on the heads of some of these weak bands ledBarrow et al. to believe that these bands may form a system analogous to theβ-system of NO and be due to a² П-² П transition. The spectrum of NS has now been studied in a little more detail by means of an uncondensed discharge through dry nitrogen and sulphur vapour in the presence of argon and thirty three bands belonging to this system have been recorded in the region 2280 to 2760 Å. It has been found possible to represent the band heads by means of the equation

$$^v {\text{head}} {\text{ = }} \left. {_{43182 \cdot 5}^{{\text{43311}} \cdot {\text{5}}} } \right\}_{ - [1219 \cdot 20(v'' + \tfrac{1}{2}) - 7 \cdot 48(v'' + \tfrac{1}{2})^2 ].}^{ + [761 \cdot 04(v' + \tfrac{1}{2}) - 5 \cdot 10(v' + \tfrac{1}{2})^2 ]}$$     

A Mössbauer spectroscopic study of the effect of molybdenum during preparation of Nd-Fe-B magnets

Elements in atomic ratios Nd₂(Fe_0.9Mo_0.1)₁₄B were melted in an induction furnace and annealed in order to examine the effect of molybdenum during the preparation of Nd-Fe-B magnets. A phase analysis has been made from ⁵⁷ Fe Mössbauer spectroscopic measurements in the temperature range of 100 to 700 K. It is found that two iron containing phases are formed, one Mo rich Fe alloy and the other Nd-Fe(Mo)-B isostructural to Nd₂Fe₁₄B. The Nd_1.1Fe₄B₄ phase usually found in Nd-Fe-B magnets is not observed in these samples. The Curie temperature, T_c, is found to be 605(5) K from the Mössbauer as well as vibrational sample magnetometer measurements on the same sample. At low temperatures, the average hyperfine field at Fe nuclei is found to show a decrease with respect to the value for Nd₂Fe₁₄B.     

An Abnormal Vibrational Mode of Torsion Pendulum

In the experiment for the determination of the gravitational constant G,we found an abnormal vibrational mode of the torsion pendulum.The abnormal mode disappeared as a magnetic damper was introduced to the torsion pendulum system.Our experimental results also show that the magnetic damper can be used to suppress the high frequency vibrational noises to torsion pendulums effectively.     

Algebraic Hamiltonian for Vibrational Spectra of Stibine

An algebraic Hamiltonian, which in a limit can be reduced to an extended local mode model by Law and Duncan, is proposed to describe both stretching and bending vibrational energy levels of polyatomic molecules, where Fermi resonances between the stretches and the bends are considered. The Hamiltonian is used to study the vibrational spectra of stibine (SbH3). A comparison with the extended local mode model is made. Results of fitting the experimental data show that the algebraic Hamiltonian reproduces the observed values better than the extended local mode model.     

Synthesis, characterization of the pentacene and fabrication of pentacene field-effect transistors

A comprehensive understanding of the organic semiconductor material pentacene is meaningful for organic fieldeffect transistors （OFETs）. Thin films of pentacene are the most mobile molecular films known to date. This paper reported that the pentacene sample was successfully synthesized. The purity of pentacene is up to 95%. The results of a joint experimental investigation based on a combination of infrared absorption spectra, mass spectra （MS）, element analysis, x-ray diffraction （XRD） and atom force microscopy （AFM）. The authors fabricated OFET with the synthesized pentacene. Its field effect mobility is about 1.23 cm^2/（V·s） and on-off ratio is above 10^6.     

Accurate spectroscopic calculations of the 19 Λ-S states and 36 Ω states of the BC+ cation

This work computed the potential energy curves of 19 Λ-S states, which arose from the first five dissociation limits of BC⁺ cation, B⁺(¹S_g) + C(³P_g), B⁺(¹S_g) + C(¹D_g), B⁺(¹S_g) + C(¹S_g), C⁺(²P_u) + B(²P_u), and B⁺(¹S_g) + C(⁵S_u). The calculations were done for internuclear separations from 0.08 to 1.07 nm. The potential energy curves of 36 Ω states yielded from these Λ-S states were also calculated. Core-valence correlation and scalar relativistic correction, basis set extrapolation as well as Davidson correction were accounted for. Of these Λ-S states, the c¹Σ⁺, D³Π, 2¹Π, 2³Σ⁺, 2¹Δ, 3¹Σ⁺, and 4¹Σ⁺ had double wells; the 3³Π and 3¹Π states had three wells; the C³Σ^? and D³Π states were inverted with the spin-orbit coupling effect included; and the second wells of c¹Σ⁺, D³Π and 3¹Σ⁺ states, the second and the third wells of 3³Π state as well as the third well of 3¹Π state were very weakly bound, which well depths were smaller than 400 cm^?1. The spectroscopic parameters were determined for all the states. The vibrational properties were predicted only for some weakly bound states. The spin-orbit coupling effect on the spectroscopic parameters was evaluated.