Raman and Infrared Spectroscopic Study of the Borate Mineral Kaliborite

We have studied the mineral kaliborite. The sample originated from the Inder B deposit, Atyrau Province, Kazakhstan, and is part of the collection of the Geology Department of the Federal University of Ouro Preto, Minas Gerais, Brazil. The mineral is characterized by a single intense Raman band at 756 cm^?1 assigned to the symmetric stretching modes of trigonal boron. Raman bands at 1229 and 1309 cm^?1 are assigned to hydroxyl in-plane bending modes of boron hydroxyl units. Raman bands are resolved at 2929, 3041, 3133, 3172, 3202, 3245, 3336, 3398, and 3517 cm^?1. These Raman bands are assigned to water stretching vibrations. A very intense sharp Raman band at 3597 cm^?1 with a shoulder band at 3590 cm^?1 is assigned to the stretching vibration of the hydroxyl units. The Raman data are complimented with infrared data and compared with the spectrum of kaliborite downloaded from the Arizona State University database. Differences are noted between the spectrum obtained in this work and that from the Arizona State University database. This research shows that minerals stored in a museum mineral collection age with time. Vibrational spectroscopy enhances our knowledge of the molecular structure of kaliborite.     

Radiation enhanced diffusion in UO2 and (U,Pu)O2

Abstract

The radiation enhanced diffusion (coefficient D*) of U-233 and Pu-238 in UO₂ and (U, Pu)O₂ with 2.5 and 15% Pu was measured during fission in a nuclear reactor. Normal diffusion sandwiches with a thin tracer layer were used. A radio-frequency furnace allowed the temperatures to be varied between 130 and 1400°. Neutron fluxes (7 × 10¹² to 1.2 × 10¹⁴ n cm^?2 s^?1) and irradiation times (56 to 334 h) were also varied to cover ranges of fission rates [Fdot] between 7× 10¹¹ and 6.4 × 10¹³ f cm^?3 s^?1 and of doses F between 4.2 × 10¹⁷ and 3.1 × 10¹⁹ f cm³. Below ～1000°, D* was completely athermal and increased linearly with [Fdot]. It was described by D* = A[Fdot] with A = 1.2× 10^?29cm⁵. A possible temperature dependence was indicated between ～1000and 1200°. The results are explained in terms of thermal and pressure effects of fission spikes and are related with other studies of radiation damage as well as with technologically interesting processes occurring in UO₂ during irradiation.     

A high resolution FTIR spectroscopic study of the hydrogen-bonded heterodimer H3N−HCN

The spectrum of the symmetric top, hydrogen-bonded heterodimer H₃N?HCN has been recorded between 2900 and 3200cm^?1 using a high resolution FTIR spectrometer. The more intense bands are associated with the ν₂ (H?CN stretch) vibration and include hot bands associated with the low frequency modes ν₅, ν₂ and ν₁₀. Weaker difference bands of the type ν₂+(n?1) ν5?nν₅ are also observed. Analysis of the bands yields values for the band origins: ν2/0=3110·5±0·2cm^?1 and ν5/0=140±5cm^?1 and the anharmonicity constants: x _2,10=12·7±0·5cm^?1, x _2,9≈x _2,5=23±3cm^?1 and x _5,10=?5±2cm^?1. The lifetime in ν₂ with respect to vibrational predissociation, estimated from the width of the sharpest observed feature, is 100?200 ps but there is some indication that this lifetime may decrease at high J.     

Spectral,electron microscopic and chemical investigations of gamma-induced purple color zonings in amethyst crystals from the Dursunbey-Balıkesir region of Turkey

Amethyst crystals on matrix specimens from the Dursunbey-Bal?kesir region in Turkey have five representative purple color zonings: dark purple, light purple, lilac, orchid, and violet. The purple color zonings have been analyzed with optical absorption spectra in the visible wavelength region, chemical full trace element analyses (inductively coupled plasma-atomic emission spectroscopy and inductively coupled plasma-mass spectroscopy), and scanning electron microscopic images with high magnification. It can be proposed that the production of the purple color in amethyst crystals is due to three dominant absorption bands centered at 375, 530, and 675 nm, respectively. In addition, the purple color zonings are also due to four minor absorption bands centered at 435, 480, 620, and 760 nm. X-ray diffraction graphics of the investigated amethyst crystals indicate that these crystals are composed of a nearly pure alpha-quartz phase and do not include any moganite silica phase and/or other mineral implications. Trace element analyses of the amethyst crystals show five representative purple color zonings, suggesting that the absorption bands can be mainly attributed to extrinsic defects (chemical impurities). However, another important factor that influences all structural defects in amethyst is likely to be the gamma irradiation that exists during amethyst crystallization and its inclusion in host materials. This gamma irradiation originates from the large underlying intrusive granitoid body in the region of amethyst formation. Irradiation modifies the valence values of the impurity elements in the amethyst crystals. It is observed that the violet-colored amethyst crystals have the most stable and the least reversible coloration when exposed to strong light sources. This situation can be related to the higher impurity content of Fe (2.50 ppm), Co (3.1 ppm), Ni (38 ppm), Cu (17.9 ppm), Zn (10 ppm), Zr (3.9 ppm), and Mo (21.8 ppm).     

Vibrational Spectroscopic Characterization of the Arsenate Mineral Barahonaite: Implications for the Molecular Structure

The mineral barahonaite is in all probability a member of the smolianinovite group. The mineral is an arsenate mineral formed as a secondary mineral in the oxidized zone of sulphide deposits. We have studied the barahonaite mineral using a combination of Raman and infrared spectroscopy. The mineral is characterized by a series of Raman bands at 863 cm^?1 with low wavenumber shoulders at 802 and 828 cm^?1. These bands are assigned to the arsenate and hydrogen arsenate stretching vibrations. The infrared spectrum shows a broad spectral profile. Two Raman bands at 506 and 529 cm^?1 are assigned to the triply degenerate arsenate bending vibration (F ₂, ν₄), and the Raman bands at 325, 360, and 399 cm^?1 are attributed to the arsenate ν₂ bending vibration. Raman and infrared bands in the 2500–3800 cm^?1 spectral range are assigned to water and hydroxyl stretching vibrations. The application of Raman spectroscopy to study the structure of barahonaite is better than infrared spectroscopy, probably because of the much higher spatial resolution.     

High-resolution Q-branches spectrum of C2H2 at 9366 and 9407 cm−1

The acetylene absorption spectrum in the Nd-laser range 9240–9520 cm^?1 has been recorded earlier (1), using a highly sensitive intracavity laser spectrometer. Two weak absorption perpendicular bands 2100⁰1¹ ← 0000⁰0⁰ (ν₀ = 9366.6 cm^?1) and 1200°3¹ ← 0000°0° (ν₀ = 9407.7 cm^?1) were studied and spectroscopic constants were obtained. However, the structure of the Q branches of these bands with J < 7 was unresolved because the resolution of the spectrometer was not very high.     

Unusual Bands in the Infrared Spectra of Some Chars

Abstract

When organic materials are charred at low or medium temperatures (up to about 450–500°C), their infrared (IR) spectra show a plethora of bands below about 2000 cm^?1, and there are additional bands in the OH and CH stretching regions, above about 2600 cm^?1. The in-between region, from about 2600 to 200 cm^?1, is quite “empty” (except for an occasional atmospheric CO₂ band caused by instrument imbalance). The reason for this emptiness is, simply, that there are very few species that have fundamentals in that region, as is well known from group frequency tables; and those that do absorb, such as metal hydrides, are quite unlikely to exist in organic precursors. Some overtones or combinations may appear, but these are usually very weak. We have, however, observed some bands in the empty region on several occasions.     

Vibration-rotation bands in ethane

The absorption spectrum of ethane was recorded at 0.014 cm^?1 resolution in the range 4500–6500 cm^?1 using a Fourier transform spectrometer and at room temperature. Eighteen bands could be identified and their type assigned. Upper state rotational constants are provided for the band at 5948.338 cm^?1 and Coriolis constants are obtained for most perpendicular bands. Vibrational assignments are suggested for the bands at 5948 cm^?1 (v7 + v10), 5914 cm^?1(v8 + v ₁₀+ v ₁₁), and 5852cm^?1 (v ₅+v ₁₀). All vibrational bands reported in the literature are gathered.     

Rotation spectrum and infrared fundamental bands of 123SbD3. Determination of molecular geometry and ab initio calculations of spectroscopic parameters

The high resolution infrared spectrum of ¹²³SbD₃ has been recorded in the 20–350?cm^?1 range and in the regions of the ν₁, ν₃ and ν₂, ν₄ fundamental bands centred at 1350 and 600?cm^?1, respectively. Splitting of the K′′?=?3, 6 lines have been observed both in the rotation and ro-vibration spectra. A large number of ‘perturbation allowed‘ transitions with selection rules Δ(k??l) =?±?3,?±?6, and?±?9 have been identified in all fundamental bands. Accurate ground state molecular parameters have been determined by means of a simultaneous fit of the rotational transitions and about 12?000 ground state combination differences from the infrared bands. The A and B reductions of the rotational Hamiltonian provided almost equivalent results. The molecular parameters of the ν _i ?=?1 (i?=?1???4) states were obtained as a result of the simultaneous analysis of the ν₁ (A₁)/ν₃ (E) stretching and of the ν₂ (A₁)/ν₄ (E) bending dyads. In fact, the corresponding excited states are affected by strong perturbations due to rovibrational interactions of Coriolis and k-type that have been treated explicitly in the model adopted for the analysis. Improved effective ground state and equilibrium geometries were determined for the molecule and compared to those of ¹²³SbH₃. Ab initio calculations at the coupled cluster CCSD(T) level with an energy-consistent large-core pseudopotential and large basis sets were carried out to determine the equilibrium structure, the anharmonic force field, and the associated spectroscopic constants of ¹²³SbH₃ and ¹²³SbD₃. The theoretical results are in good agreement with the experimental data.     

Effect of proton irradiation on the physical properties of PC/PBT blends

Samples from polycarbonate/poly (butylene terephthalate) (PC/PBT) blends film have been irradiated using different fluences (1?×?10¹⁵– 5?×?10¹⁷ H⁺/cm²) of 1?MeV protons at the University of Surrey Ion Beam Center, UK. The structural modi?cations in the proton irradiated samples have been studied as a function of fluence using different characterization techniques such as X-ray diffraction and UV spectroscopy. The results indicate that the proton irradiation reduces the optical energy gap that could be attributed to the increase in structural disorder of the irradiated samples due to crosslinking. Furthermore, the color intensity ΔE, which is the color difference between the non-irradiated sample and those irradiated with different proton fluences, increased with increasing the proton fluence up to 5?×?10¹⁷ H^+/cm², convoyed by an increase in the red and yellow color components. In addition, the resultant effect of proton irradiation on the thermal properties of the PC/PBT samples has been investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). It is found that the PC/PBT decomposes in one weight loss stage. Also, the variation of transition temperatures with proton fluence has been determined using DSC. The PC/PBT thermograms were characterized by the appearance of two endothermic peaks due to the glass transition and melting temperatures. The melting temperature of the polymer, T_m, was investigated to probe the crystalline domains of the polymer, since the proton irradiation destroys the crystalline structure so reducing the melting temperature.     

Laser-induced Raman scattering in calcium titanate

The Raman spectrum of polycrystalline calcium titanate prepared by a liquid mix technique and heated to 800°C has been recorded at room temperature using an argon-ion laser as exciter. The observed spectrum was interpreted on the basis of factor-group C_2V. Not all of the Raman active modes predicted by factor group analysis were observed and this could be due to: over-lapping of bands, or very low polarizabilities of some of the modes or masking of the weak bands by intense bands. The band at 639 cm^?1 is tentatively assigned to the TiO symmetric stretching vibration (γ₁) and the bands at 495 and 471 cm^?1 to torsional modes. The bands in the region 180–340 cm^?1 are assigned to the OTiO bending modes and the 155 cm^?1 band to the Ca(TiO₃) lattice mode. The observed Raman bands are compared with the available infrared absorption data and, as expected, some coincidences in frequencies are seen for this compound with a noncentrosymmetric structure.     

Kinetics of radiation polymerization of vinyl benzoate

Abstract

Vinyl benzoate was polymerized by γ-radiation from a cobalt-60 source and the kinetics of polymerization were studied at several temperatures. The results showed that the rate of polymerization was proportional to I^0.66 , where I is the radiation dose rate. The net activation energy for the polymerization reaction, (E_p -1/2 E_t ), was found to be 3.62 kcal, where E_p and E_t are the activation energies for the propagation and termination stages of the reaction. The radical yield measured by the loss of DPPH in the solution after irradiation was G=5.0, while the G (Radical) effective in initiating polymerization was 0.94. The ratio of the rate constants, k² _p/k_t = 5.8 × 10^?4 at 60° and 1.59 × 10^?4 at 25° The rate of polymerization was higher than that of styrene but lower than that of vinyl acetate under comparable conditions.     

Investigation of the temperature dependence for the spectra of supercooled water in the middle infrared

The temperature dependence of the bending ν₂, combination ν₂ + ν _L , and stretching (ν₁, ν₃, 2ν₂) absorption bands in the infrared spectra of supercooled water with a temperature-change step Δt from 2 to 2.5°C was studied using an advanced infrared Fourier spectrometer. It was found that the frequency of the maximum of the stretching absorption band (2700–3700 cm^?1) decreases with the reduction of the water temperature from ?0.5 to ?5.0°C. The frequency of the maximum of the combination absorption band (2130 cm^?1) increases with the reduction of the water temperature in a range from ?3.0 to ?5.0°C. The frequency of the maximum of the absorption band of bending oscillation (1640 cm^?1) is invariable with a reduction of the water temperature from ?0.5 to ?5.0°C.     

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.     

A Vibrational Spectroscopic Study of the So-Called Healing Mineral Papagoite CaCuAlSi2O6(OH)3

ABSTRACT

Papagoite is a silicate mineral named after an American Indian tribe and was used as a healing mineral. Papagoite CaCuAlSi₂O₆(OH)₃ is a hydroxy mixed anion compound with both silicate and hydroxyl anions in the formula. The structural characterization of the mineral papagoite remains incomplete. Papagoite is a four-membered ring silicate with Cu²⁺ in square planar coordination.

The intense sharp Raman band at 1053 cm^?1 is assigned to the ν₁ (A _1g) symmetric stretching vibration of the SiO₄ units. The splitting of the ν₃ vibrational mode offers support to the concept that the SiO₄ tetrahedron in papagoite is strongly distorted. A very intense Raman band observed at 630 cm^?1 with a shoulder at 644 cm^?1 is assigned to the ν₄ vibrational modes.

Intense Raman bands at 419 and 460 cm^?1 are attributed to the ν₂ bending modes.

Intense Raman bands at 3545 and 3573 cm^?1 are assigned to the stretching vibrations of the OH units. Low-intensity Raman bands at 3368 and 3453 cm^?1 are assigned to water stretching modes. It is suggested that the formula of papagoite is more likely to be CaCuAlSi₂O₆(OH)₃ · xH₂O. Hence, vibrational spectroscopy has been used to characterize the molecular structure of papagoite.     

Atmospheric chemistry of diazomethane – an experimental and theoretical study

The kinetics of the O₃, OH and NO₃ radical reactions with diazomethane were studied in smog chamber experiments employing long-path FTIR and PTR-ToF-MS detection. The rate coefficients were determined to be k _CH2NN+O3?=?(3.2?±?0.4)?×?10^?17 and k _CH2NN+OH?=?(1.68?±?0.12)?×?10^?10 cm³ molecule^?1 s^?1 at 295?±?3?K and 1013?±?30 hPa, whereas the CH₂NN?+?NO₃ reaction was too fast to be determined in the static smog chamber experiments. Formaldehyde was the sole product observed in all the reactions. The experimental results are supported by CCSD(T*)-F12a/aug-cc-pVTZ//M062X/aug-cc-pVTZ calculations showing the reactions to proceed exclusively via addition to the carbon atom. The atmospheric fate of diazomethane is discussed.     

Raman spectroscopic study of the antimonate mineral lewisite (Ca,Fe, Na)2(Sb,Ti)2O6(O,OH)7

The mineral lewisite, (Ca, Fe, Na)₂(Sb, Ti)₂O₆(O, OH)₇, an antimony-bearing mineral, has been studied by Raman spectroscopy. A comparison is made with the Raman spectra of other minerals, including bindheimite, stibiconite, and roméite. The mineral lewisite is characterised by an intense sharp band at 517 cm^?1 with a shoulder at 507 cm^?1 assigned to SbO stretching modes. Raman bands of medium intensity for lewisite are observed at 300, 356, and 400 cm^?1. These bands are attributed to OSbO bending vibrations. Raman bands in the OH stretching region are observed at 3200, 3328, 3471 cm^?1, with a distinct shoulder at 3542 cm^?1. The latter is assigned to the stretching vibration of OH units. The first three bands are attributed to water stretching vibrations. The observation of bands in the 3200–3500 cm^?1 region suggests that water is involved in the lewisite structure. If this is the case then the formula may be better written as (Ca, Fe²⁺, Na)₂(Sb, Ti)₂(O, OH)₇ xH₂O.     

Measurement of integrated intensities of acetylene bands at 3·04, 7·53 and 13·7 μm

Integrated intensities of acetylene bands at 3·04, 7·53 and 13·7 μm have been measured at 300°K using the Wilson-Wells-Penner-Weber technique and a spectral resolution of 0·6 cm^?1. Our best estimates of the intensities are 294 ± 6 cm^?2atm^?1 for the 3·04 μ bands, 87 ± 2 cm^?2atm^?1forthe 7·53 μband and 729 ± 28 cm^?2atm^?1 for the 13·7 μ band at 300°K.     

High resolution infrared study of the parallel band ν3 of chloroform CH35 Cl3

The infrared spectrum of chloroform in the region of the parallel fundamental band ν₃ around 367 cm^?1 has been measured with a Fourier spectrometer at a resolution of 0.001 cm^?1. An isotopically pure sample of CH³⁵Cl₃ was used. More than 5000 lines were assigned in the ν₃ band. A reanalysis of the ground state constants was performed by combining 1671 combination differences from this work, 712 differences from a previous study of the ν₂ band, and 80 millimetre wave lines from the literature. In the analysis of the ν₃ band, a model of an unperturbed symmetric top band was applied. The data were fitted with a standard deviation of 0.18 × 10^?3 cm^?1, and the following leading parameters were obtained: ν₀ = 367.295 550(8) cm^?1, B ₃—B ₀ = ?77.058(4) × 10^?6 cm^?1 and C ₃—C ₀ = ?18.600(11) × 10^?6 cm^?1. In addition, several hot bands have been studied. The isotopic effects were studied also by analysing spectra of the isotopically natural sample.     

Evaporated a-Si films with low ESR defect density by hydrogenation under NH3 ambient

a-Si films were obtained by a reactive evaporation of Si atoms with an electron gun, under a NH₃ ambient of 5 × 10^?5 torr. The H introduced amount efficiently reduces the ESR dangling bond density from 4 × 10¹⁹ cm^?3 in pure samples to 2 × 10¹⁷ cm^?3. The hydrogen presence is evidence by both the Si-H infrared bands and the strong spin-density increase with annealing. This increase, beginning at a temperature of 350°C, is attributed to the H effusion. XPS measurements show also an incorporation of bonded nitrogen.