Raman Spectrum of Chloromethyl Thiocyanate

Abstract

The liquid-state Raman spectrum was obtained for chloromethyl thiocyanate. The previously unobserved C-S-C bending band was observed at 188 cm^?1. The Raman spectrum supports the conclusion that only the C_S conformer is present.     

The Nanosecond Laser Flash Photolysis (LFP) Transient Spectra of Aqueous CCl4 Solution

Abstract

The Raman spectrum of polycrystalline vaterite is presented and compared to spectra of calcite and aragonite, the other two common CaCO₃ polymorphs; Raman spectroscopy easily distinguishes between these three polymorphs. An important feature of the Raman spectrum of vaterite is splitting of both the ν₁ and ν₄ peaks. The splitting of the ν1 peak implies two distinct site symmetries for the CO₃ ^?2 groups. A definitive crystal structure determination of vaterite is not yet available, but none of the three proposed structures for vaterite show such a feature.     

Vibrational Spectrum of Bromal

Abstract

The molecular structure of tribromoacetaldehyde, Bromal, has been studied by Ab Initio theoretical calculations. The IR spectrum has been recorded in the range 4000–200 cm^?1. The Raman spectrum has been studied with a SPEX 1403 spectrometer using the 5145Å exciting line of a Spectra-Physics 164 Ar ion laser. Depolarization ratios were also measured. The fundamental vibrations of Br₃ CCOH and also some overtones, combinations and difference bands were assigned.     

Vibrational Spectrum of Tribromoethanol

Abstract

The molecular structure of tribromoethanol has been studied by Ab Initio theoretical calculations. The IR spectrum has been recorded in the range 4000—200 cm^?1. Whereas, the Raman spectrum has been determined by means of a SPEX 1403 spectrometer using the 5145Å exciting line of a Spectra—Physics 164 Ar ion laser. Depolarization ratios were also measured. The fundamental vibrations of CBr₃CH₂OH as well as some overtones, combinations and difference bands were assigned.     

Temperature Effects in the Raman Spectrum of Solid Orthocarborane

Abstract

Variable temperature studies of the laser Raman spectrum of solid orthocarborane indicate a change in the line widths of the peaks in the observed frequency region from 745 cm^?1 to 815 cm^?1. A marked change in the line width of the 807 cm^?1 peak around 4°C confirms recently observed anomalies in the NMR spectrum at this temperature.     

Vibrational spectroscopic characterization of the magnesium borate-phosphate mineral lüneburgite

ABSTRACT

Lüneburgite, a rare magnesium borate-phosphate mineral from Mejillones, Chile, has been characterized using Raman and mid-infrared spectroscopy methods. Boron tetrahedra are characterized by sharp Raman band at 877?cm^?1, attributed to the ν₁[BO₄]^5? symmetric stretching mode. The phosphate anion is associated with a distinct band at 1032?cm^?1, attributed to the ν₃[PO₄]^3? antisymmetric stretching mode. The most intensive Raman band at 734?cm^?1 is ascribed to stretching vibrations of bridging oxygen atoms in boron–oxygen–phosphor bridges. Bonds associated with water bending mode and stretching vibration are observed at 1661?cm^?1 (infrared) and in the 3000–3500?cm^?1 region (Raman and infrared spectrum).     

V centers produced in KI crystals under KrCl excimer laser irradiation

Abstract

Irradiation of KI near 150 K with KrCl excimer laser irradiation (hv=5. 58 eV) produces V centers causing V₂ and V₃ bands. The two bands exhibit 100-type dichroism. In KI containing V centers, the 111 cm^?1 Raman signal attributed to I_3- molecular ions is observed. Under KrCl excimer laser irradiation at low temperatures, resonance Raman scattering effects have been also studied for KI, NaI and LiI.     

Pressure and photo-induced phase transitions in sulphur investigated by Raman spectroscopy

Abstract

The phase transition of orthorhombic sulphur α-S₈ to a high pressure amorphous sulphur allotrope (a-S) has been investigated by Raman spectroscopy. The conversion is found to be induced by the absorption of laser light and can be discussed in terms of ring opening followed by cis-trans conversion of the dihedral angle of S₈ molecules. Laser energy and transition pressure are correlated due to the pressure tuned red shift of the absorption edge of α-S₈. The amorphous (a-S) phase is observed up to 15 GPa at laser intensities below 30μW/μm² at 514.5 and 488.0 nm. Above this threshold power a-S transforms into a second photo-induced phase (p-S), whose discrete Raman spectrum implies an ordered molecular and crystalline structure. By further increasing pressure crystalline S₆ can be created which is found to be the dominant molecular species at pressures above 10 GPa and low temperatures. A phase diagram in the range T < 300 K and p < 15 GPa is also presented.     

Raman Study of the Effect of NaClO4 and NaI on the Hydrogen-Bonded Structure of Liquid NH3

Abstract

Recent studies^1,2 of the Raman spectra of liquid ammonia have been in disagreement with regard to the assignment of bands in the 3000 cm^?1 region. This region is complicated by Fermi resonance between the ν₁ (A₁) fundamental stretching mode and the 2ν₄ (A₁) overtone of the bending mode. In an effort to help clarify these assignments and to study further the structure of liquid ammonia, it was decided to measure the Raman spectrum of several salt solutions in liquid ammonia.     

Effects of composition ratio on structure and phase transition of ferroelectric nanocomposites from silicon dioxide nanoparticles and triglycine sulfate

The present work is devoted to study on influences of silicon dioxide nanoparticles (SiO₂) on structure and phase transition of a classical ferroelectric of triglycine sulfate (TGS) by synthesizing a composite containing SiO₂ and TGS at different composition weight ratios. Particle size analysis, X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) techniques were utilized to charaterize the synthesized composite. The experiments for investigation of phase transition were conducted from 20 to 120°C under a weak electric field (1?V.cm^?1) at 1?kHz. The results revealed an expansion of ferroelectric phase of TGS by 15–55°C with increasing the SiO₂ content. Besides, an additional phase transition point which is characteristic for the bulk clusters of TGS was found at low content of SiO₂. The detected anomalies were discussed thoroughly based on the interaction between components in the composite.     

Two-phonon Raman scattering in GaAs

The second-order Raman Spectrum of GaAs has been measured at room temperature by using an argon ion laser with Brewster's angle configuration. A number of critical points have been interpreted by considering neutron inelastic scattering work and detailed critical-point analysis in Ge. The Γ₁ component is the strongest in the spectrum where overtone scattering is dominant. Combination scattering has been observed in the energy region between 300 and 350 cm^?1for both Γ₁ and Γ₁₅ components. The second-order Raman spectrum is compared with the two-phonon overtone Raman intensity, calculated from neutron diffraction data. In the low frequency region, the Raman spectrum shows directly the one-phonon density of states of the TA phonon.     

Electronic structure and related properties of the ferroelectric crystal triglycine sulfate

The electronic band structure and related physical properties of the crystal triglycine sulfate (TGS), (NH₂CH₂COOH)₃·H₂SO₄, in the ferroelectric phase P2₁ have been calculated using the first principles Linear Combination of Atomic Orbitals (LCAO) code CRYSTAL’06 at the B3LYP level of theory. The interactions between the quasi-separate three glycine groups and the sulfate complex have been studied by the analysis of the density of states of the crystal. The glycine 2 group was found to be the zwitterion in the optimized structure. Ten coefficients of the elastic stiffness tensor c_kl, four coefficients of the tensor of the elastoelectrical effect e_ki, and the spontaneous polarization P_s of TGS have been calculated for the first time and have been found to agree well with experimental data. Extrema are found in the elastoelectric coefficient e₂₂ as a function of the strain ε₂, and in the spontaneous polarization P_s as a function of the unit cell volume.     

Raman Spectroscopic Analysis of Perovskite-Structured Alkali Metal Fluorides Containing Nickel and Copper Ions

ABSTRACT

The mixed metal fluorides containing alkali metals have a range of important applications in optical and electronic devices. Raman spectrums of two such fluorides were examined. Raman spectrum of KCuF₃ at 300 K exhibited bands at 261, 295, 363, 468, 519, and 549 cm^?1, indicating site symmetry (orthorhombic) lower than the tetragonal symmetry as observed from the powder X-ray diffraction pattern. Cubic KNiF₃ showed bands at 410, 468, and 657 cm^?1. The first two bands were attributed to the second-order phonon scattering, and the band at 657 cm^?1 was assigned to two-magnon peak.     

Inverse Raman spectra of SBN40+Pr3+

Inverse Raman spectra of rare-earth ion doped SBN40 [Ba_0.4Sr_0.6Nb₂O₆:Pr³⁺(1.0 weight%)] are obtained over a range 0 to 950 cm^?1 using an Ar ion laser and a pulse-dye laser with 0.2 micros pulsewidth. The spectra are in agreement with the results obtained by the normal Raman scattering. It is found that a single-shot IRS is possible to obtain the Raman spectrum within laser exposuring time, if it is a sharp one.     

Photo-and pressure-induced transformations in the linear orthorhombic polymer of C<Subscript>60</Subscript>

Stability of the linear orthorhombic polymer of C₆₀ under pressure and laser irradiation is studied by Raman scattering and X-ray diffraction measurements. The Raman spectrum at ambient pressure remains unchanged, in the time scale of the experiment, up to an intensity of 3200 W/cm² of the 514.5 nm line of an Ar⁺ laser, but irreversible changes are observed at higher intensities. The Raman spectra recorded at increased pressure show similar irreversible changes even at the laser intensity as low as 470 W/cm². The X-ray diffraction and Raman measurements of the pressure-treated samples, performed after pressure release, show that the nonirradiated material does not exhibit any changes in the crystal structure and phonon spectra. This behavior indicates a pressure-enhanced photo-induced transformation to a new polymeric phase characterized by a Raman spectrum that differs from those of the other known polymeric phases of C₆₀. The Raman spectra of the phototransformed linear orthorhombic polymer of C₆₀ were measured at a pressure of up to 29 GPa. The pressure dependence of the Raman mode frequencies show singularities near 4 GPa and 15 GPa, respectively, related to a reversible phase transition and an irreversible transformation to a metastable disordered phase. The diffuse Raman spectrum of the disordered phase does not exhibit substantial changes with an increase in pressure up to 29 GPa. The high-pressure phase transforms to a mixture of pristine and dimerized C₆₀, after pressure release and exposure to ambient conditions for 30 h. The text was submitted by the authors in English.     

The Raman Spectrum of Mercury (II) Iodide in High Temperature Solvents

Abstract

The Raman spectrum of mercury(II) iodide was observed in cesium nitrate at 430°C and in meta- and para-terphenyl at 235 and 240°C, respectively. A single strong polarized line was found at 148. 5 cm^?1, width at half height 15 cm^?1 in cesium nitrate, and a single line at 154. 0 cm^?1 width at half height 7 cm^?1 in the terphenyls. The observed spectra are not consistent with interactions of the solute and the solvents involving bonds of highly covalent character, but do not exclude other interactions.

In the course of an investigation on the nature of mercury (II) iodide species in solution in molten alkali metal nitrates, by its distribution between the salt melts and terphenyl melts^{1, 2}, it became of interest to study by means of Raman spectroscopy the mercury (II) iodide species formed. Several such studies at lower temperatures have already been made: in the gas phase³, in a krypton matrix⁴, in alcohols⁵, tributy phosphate⁶ and dioxame⁷, and in molten mercury(II) iodide⁸, chloride⁹, and bromide⁹. The reason for looking at the Raman spectrum in yetfurther media was the suggestion made on the basis of thermodynamic and kinetic data^2,10 that the mercury(II) iodide species in the alkali mitrate melts are solvated by nitrate anions, and that possiby the mixed anion terrahedral species HgI₂(NO₃)₂ is formed. Recent Ranan sepctrophotometric data on mixed halide anionic complexes of mercury₁₁ identified prominent lines of the spectrum of the species HgBr_nI^2– _4–n, including HGBr₂I₂ ^2–, so that a comparison could be made. The solubility of mercury (II) iodide in molten alkali metal nitrates is rather small, expect for cesium nitrate¹², Where the solubility should be sufficent for the Raman spectrum to be recorded. Also, it was comcluded from vapor pressure osmometric data in aromatic solvents that demiric species of mercury(II) halides (even a trimeric species of the iodide) are found, in which the mercury has a distorted octahedral coordination, with three halogen atoms bonded to a mercury atom in the dimer¹³. In terphenyl melts, the solubility     

A Vibrational Spectroscopic Study of the Sulfate Mineral Glauberite

The mineral glauberite is one of many minerals formed in evaporite deposits. The mineral glauberite has been studied using a combination of scanning electron microscopy with energy dispersive X-ray analysis and infrared and Raman spectroscopy. Qualitative chemical analysis shows a homogeneous phase, composed by sulfur, calcium, and sodium. Glauberite is characterized by a very intense Raman band at 1002 cm^?1 with Raman bands observed at 1107, 1141, 1156, and 1169 cm^?1 attributed to the sulfate ν₃ antisymmetric stretching vibration. Raman bands at 619, 636, 645, and 651 cm^?1 are assigned to the ν₄ sulfate bending modes. Raman bands at 454, 472, and 486 cm^?1 are ascribed to the ν₂ sulfate bending modes. The observation of multiple bands is attributed to the loss of symmetry of the sulfate anion. Raman spectroscopy is superior to infrared spectroscopy for the determination of glauberite.     

Characterization of uranium tetrafluoride (UF4) with Raman spectroscopy

The Raman spectrum of uranium tetrafluoride (UF₄) is unambiguously characterized with multiple Raman excitation laser sources for the first time. Across different laser excitation wavelengths, UF₄ demonstrates 16 distinct Raman bands within the 50–400 cm⁻¹ region. The observed Raman bands are representative of various F–F vibrational modes. UF₄ also shows intense fluorescent bands in the 325–750 nm spectral region. Comparison of the UF₄ spectrum with the ZrF₄ spectrum, its crystalline analog, demonstrates a similar Raman band structure consistent with group theory predictions for expected Raman bands. Additionally, a demonstration of combined scanning electron microscopy and in situ Raman spectroscopy microanalytical measurements of UF₄ particulates shows that despite the inherent weak intensity of Raman bands, identification and characterization are possible for micron‐sized particulates with modern instrumentation. The published well‐characterized UF₄ spectrum is extremely relevant to nuclear materials and nuclear safeguard applications. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. Journal of Raman Spectroscopy published by John Wiley & Sons Ltd.     

Laser Raman Spectra of Crystalline Chloromercurate(II) Complexes

Abstract

The laser Raman spectra of crystalline [(CH₃)₄N] HgCl₃ and [(CH₃)₄N]₂HgCl₄ have been studied in the 400–20 cm^?1 region. All expected Raman active modes for the HgCl₃ ^? and HgCl₄ ^?2 ions are observed and assignments of the vibrational frequencies are made in relation to the structure of the anions.     

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.