Vibrational spectroscopy of the sorosilicate mineral hemimorphite Zn4(OH)2Si2O7 · H2O

Raman spectroscopy complimented by infrared spectroscopy has been used to study the mineral hemimorphite from different origins. The Raman spectra show consistently similar spectra with only one sample showing additional bands due to the presence of smithsonite. Raman bands observed at 3510–3565 and 3436–3455 cm⁻¹ are assigned to OH stretching vibrations. Using a Libowitzky type formula, these OH bands provide hydrogen bond distances of 0.2910, 0.2825, 0.2762 and 0.2716 pm. Water bending modes are observed in the Raman spectrum at 1633 cm⁻¹. An intense Raman band at 930 cm⁻¹ is attributed to SiO symmetric stretching vibration of the Si₂O₇ units. Raman bands observed at 451 and 400 cm⁻¹are attributed to out-of-plane bending vibrations of the Si₂O₇ units. Raman bands at 330, 280, 168 and 132 cm⁻¹ are assigned to ZnO and OZnO vibrations.     

A Raman spectroscopic study of the antimonite mineral peretaite Ca(SbO)4(OH)2(SO4)2·2H2O

Raman spectra of mineral peretaite Ca(SbO)₄(OH)₂(SO₄)₂·2H₂O were studied, and related to the structure of the mineral. Raman bands observed at 978 and 980 cm^?1 and a series of overlapping bands observed at 1060, 1092, 1115, 1142 and 1152 cm^?1 are assigned to the SO₄^2? ν₁ symmetric and ν₃ antisymmetric stretching modes. Raman bands at 589 and 595 cm^?1 are attributed to the SbO symmetric stretching vibrations. The low intensity Raman bands at 650 and 710 cm^?1 may be attributed to SbO antisymmetric stretching modes. Raman bands at 610 cm^?1 and at 417, 434 and 482 cm^?1 are assigned to the SO₄^2? ν₄ and ν₂ bending modes, respectively. Raman bands at 337 and 373 cm^?1 are assigned to O–Sb–O bending modes. Multiple Raman bands for both SO₄^2? and SbO stretching vibrations support the concept of the non-equivalence of these units in the peretaite structure.     

Resonance raman spectra of würster's cation dimers: p-phenylenediamine and 2,3,5,6-tetramethyl-p-phenylenediamine

Resonance Raman spectra have been observed for the dimers of p-phenylenediamine cation (PPD⁺) and of 2,3,5,6-tetramethyl-p-phenylenediamine cation (TMPD⁺). When the exciting light frequency approached the absorption bands characteristic of the dimers, new polarized Raman lines appeared at 161 cm^?1 for (PPD⁺)₂ and at 117 cm^?1 for (TMPD⁺)₂ with a striking resonance enhancement. The resonant behaviour as well as the frequency values indicate that they are reasonably assigned to the interradical stretching vibrations of the parallel D_2h dimer molecules.     

LiO Raman Bands of 6Li2CO3 and 7Li2CO3

The Raman spectra of polycrystalline ⁶Li₂CO₃ have been recorded in the frequency region from 600 to 300 cm⁻¹. Four very weak bands have been observed for each compound the isotopic frequency shifts are reported. The results have been compared with those from the i.r. spectra for the LiO₄ tetrahedra.     

Etude Raman de l'oxy-pentasulfure de gallium et de trilanthane GaLa3OS5

The polarized Raman spectra of La₃GaOs₅ in single crystal form have been investigated in the 50–700 cm⁻¹ frequency. An interpretation of the observed bands is given.     

Synthesis and vibrational spectroscopic characterisation of synthetic hydrozincite and smithsonite

Hydrozincite and smithsonite were synthesised by controlling the partial pressure of CO₂. Previous crystallographic studies concluded that the structure of hydrozincite was a simple one. However both Raman and infrared spectroscopy show that this conclusion is questionable. Multiple bands are observed in both the Raman and infrared spectra in the (CO₃)²⁻ antisymmetric stretching and bending regions of hydrozincite showing that the symmetry of the carbonate anion is reduced and in all probability the carbonate anions are not equivalent in the hydrozincite structure. Multiple OH stretching vibrations centred in both the Raman and infrared spectra show that the OH units in the hydrozincite structure are non-equivalent. The Raman spectrum of synthetic smithsonite is a simple spectrum characteristic of carbonate with Raman bands observed at 1408, 1092 and 730 cm⁻¹.     

The structure of mimetite,arsenian pyromorphite and hedyphane – A Raman spectroscopic study

The minerals mimetite Pb₅(AsO₄)₃Cl, arsenian pyromorphite Pb₅(PO₄,AsO₄)₃Cl and hedyphane Pb₃Ca₂(AsO₄)₃Cl have been studied by Raman spectroscopy complimented with infrared spectroscopy. Mimetite is characterised by a band at 812–3 cm⁻¹ attributed to the A_g mode. For the arsenian pyromorphite this band is observed at 818 cm⁻¹ and for hedyphane at 819 cm⁻¹. For mimetite and hedyphane bands at 788 and 765 cm⁻¹ are attributed to A_u and E_1u vibrational modes and are both Raman and infrared active. For the arsenian pyromorphite, Raman bands at 917–1014 cm⁻¹ are attributed to phosphate stretching vibrations. Raman spectroscopy clearly identifies bands attributable to isomorphous substitution of arsenate by phosphate. The observation of low intensity bands in the 3200–3550 cm⁻¹ region are assigned to adsorbed water and OH units, thus indicating some replacement of chloride ions with hydroxyl ions.     

A Raman spectroscopic study of the mineral coquandite Sb6O8(SO4)·(H2O)

Raman spectra of coquandite Sb₆O₈(SO₄)·(H₂O) were studied, and related to the structure of the mineral. Raman bands observed at 970, 990 and 1007 cm^?1 and a series of overlapping bands are observed at 1072, 1100, 1151 and 1217 cm^?1 are assigned to the SO₄^2? ν₁ symmetric and ν₃ antisymmetric stretching modes respectively. Raman bands at 629, 638, 690, 751 and 787 cm^?1 are attributed to the SbO stretching vibrations. Raman bands at 600 and 610 cm^?1 and at 429 and 459 cm^?1 are assigned to the SO₄^2? ν₄ and ν₂ bending modes. Raman bands at 359 and 375 cm^?1 are assigned to O–Sb–O bending modes. Multiple Raman bands for both SO₄^2? and SbO stretching vibrations support the concept of the non-equivalence of these units in the coquandite structure.     

Study of alkali halide/FHF− systems at 10 – 290 K, 0 – 8 kBAR

The bifluoride ion FHF^?, (and FDF^?), has been substitutionally isolated within single crystal samples of several alkali halides. Infrared and Raman spectra of these crystals have been studied at variable temperature and pressure. The infrared absorptions are strong, whereas the Raman is weak. At low temperatures the bands are very sharp with halfwidths less than 1 cm^?1. On applying pressure, ^ν₃ increases in frequency whereas ^ν₂ decreases. On reducing temperature, ^ν₃ decreases in frequency whereas ^ν₂ increases. Hence the effect of volume contraction is overridden in the temperature dependent case. The deuterated spectra confirm that the bifluoride ion is well isolated within the alkali halide matrix.     

Vibrational spectroscopic study of syngenite formed during the treatment of liquid manure with sulphuric acid

Syngenite (K₂Ca(SO₄)₂·H₂O), formed during treatment of manure with sulphuric acid, was studied by infrared, near-infrared (NIR) and Raman spectroscopy. C_s site symmetry was determined for the two sulphate groups in syngenite (P2₁/m), so all bands are both infrared and Raman active. The split ν₁ (two Raman+two infrared bands) was observed at 981 and 1000 cm⁻¹. The split ν₂ (four Raman+four infrared bands) was observed in the Raman spectrum at 424, 441, 471 and 491 cm⁻¹. In the infrared spectrum, only one band was observed at 439 cm⁻¹. From the split ν₃ (six Raman+six infrared) bands three 298 K Raman bands were observed at 1117, 1138 and 1166 cm⁻¹. Cooling to 77 K resulted in four bands at 1119, 1136, 1144 and 1167 cm⁻¹. In the infrared spectrum, five bands were observed at 1110, 1125, 1136, 1148 and 1193 cm⁻¹. From the split ν₄ (six infrared+six Raman bands) four bands were observed in the infrared spectrum at 604, 617, 644 and 657 cm⁻¹. The 298 K Raman spectrum showed one band at 641 cm⁻¹, while at 77 K four bands were observed at 607, 621, 634 and 643 cm⁻¹. Crystal water is observed in the infrared spectrum by the OH-liberation mode at 754 cm⁻¹, OH-bending mode at 1631 cm⁻¹, OH-stretching modes at 3248 (symmetric) and 3377 cm⁻¹ (antisymmetric) and a combination band at 3510 cm⁻¹ of the H-bonded OH-mode plus the OH-stretching mode. The near-infrared spectrum gave information about the crystal water resulting in overtone and combination bands of OH-liberation, OH-bending and OH-stretching modes.     

Surface-enhanced raman scattering from poly(4-vinyl pyridine)

Surface-enhanced Raman scattering (SERS) has been observed for poly(4-vinyl pyridine) absorbed onto silver island films. Bands near 1219 and 1613 cm^?1, which are weak in normal Raman spectra of PVP, are strong in SERS spectra, and the band near 1020 cm^?1, which is the strongest band in the normal spectra, is relatively weak in SERS. The strongest bands in the SERS spectra all belong to the same symmetry species as α_ZZ, implying that the pyridine moieties are adsorbed through the nitrogen atoms with a vertical conformation. The ring breathing mode of the pyridine rings is observed near 1020 cm^?1, a frequency characteristic of pyridinium ions or coordinated pyridine, providing further evidence for adsorption through the nitrogen atoms. Silver catalyzed photooxidation, which can lead to the appearance of artifacts in SERS spectra, particularly of polymers, can be reduced by overcoating SERS samples with thin films of polymers such as poly(methyl methacrylate) that have low Raman scattering cross sections.     

Raman spectral study of solid and dissolved poly(vinyl alcohol) and ethylene-vinyl alcohol copolymer

We have measured the Raman spectra of ethylene-vinyl alcohol copolymer (EVOH) and poly(vinyl alcohol) (PVOH). Spectra of 88% hydrolyzed PVOH were examined from the partially crystalline solid, from PVOH dissolved in both H₂O and D₂O, and from films precipitated from these solutions. The spectrum in H₂O differs from that of the starting material by disappearance of sharp bands having Raman shift values of 1146 and 1093 cm^?1, strengthening of a band near 915 cm^?1, decrease in frequency of bands at 480, 1356, and 1441 cm^?1, and increase in frequency of bands at 369, 413, 1023, 1371, and 2910 cm^?1. The spectrum of the film shows partial reversal of these trends. With D₂O as the solvent, the band shifts are slightly different from those listed above and new bands appear. These changes are indicative of loss of crystallinity, change in stereochemistry, and partial deuteration of hydroxyl during dissolution of this PVOH sample at room temperature. © 1994 John Wiley & Sons, Inc.     

Thermal decomposition of liebigite

Summary A combination of high resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer has been used to study the thermal decomposition of liebigite. Water is lost in two steps at 44 and 302°C. Two mass loss steps are observed for carbon dioxide evolution at 456 and 686°C. The product of the thermal decomposition was found to be a mixture of CaUO₄ and Ca₃UO₆. The thermal decomposition of liebigite was followed by hot-stage Raman spectroscopy. Two Raman bands are observed in the 50°C spectrum at 3504 and 3318 cm^-1 and shift to higher wavenumbers upon thermal treatment; no intensity remains in the bands above 300°C. Three bands assigned to the υ₁ symmetric stretching modes of the (CO₃)^2- units are observed at 1094, 1087 and 1075 cm^-1 in agreement with three structurally distinct (CO₃)^2- units. At 100°C, two bands are found at 1089 and 1078 cm^-1. Thermogravimetric analysis is undertaken as dynamic experiment with a constant heating rate whereas the hot-stage Raman spectroscopic experiment occurs as a staged experiment. Hot stage Raman spectroscopy supports the changes in molecular structure of liebigite during the proposed stages of thermal decomposition as observed in the TG-MS experiment.     

Raman spectrum from a single crystal of SnHPO4

The polarized Raman spectrum of a single crystal of SnHPO₄ has been obtained in order to ascertain the vibrational characteristics of HPO²⁻₄ dimers in a known configuration. Bands due to hydroxyl, OH, stretching, POH bending and the hydrogen bond were observed in addition to most of the predicted lattice modes.The OH stretching mode was observed at 2730 cm⁻¹, the in-plane POH bend at 1275 cm⁻¹ and the out-of-plane POH bend at 818 cm⁻¹. A band of 55 cm⁻¹ is assigned, on the basis of its deuterium shift, to a deformation of the hydrogen bond. Very low frequency bands at 18 and 30 cm⁻¹ reflect the layer structure of SnHPO₄ in which intra-layer forces are strong and inter-layer (hydrogen bonds) forces are weak.     

Vibrational levels and anharmonicity in SF6—I. Vibrational band analysis

The vibrational spectrum of SF₆ has been recorded with a Fourier-transform i.r. spectrometer at a resolution of 0.05 cm⁻¹ and pressure—path length products of up to 2 × 10⁵ Torr-cm. Twenty-nine bands were observed. Rotational structure was resolved for 11 of these and polynomials were fitted to the observed frequencies to yield the scalar spectroscopic constants, including the band origins m and derived values of B′B₀ and the Coriolis constants ζ. For 12 other unresolved bands accurate estimates of the origins could be made from the frequency of a sharp Q-branch edge. Three more bands (ν₃, 2ν₁ + ν₃, and 3ν₃) were not resolvable at our resolution but have been previously analyzed from Doppler-limited or sub-Doppler spectra. In addition, about 10 assignable hot bands were observed whose frequency shifts relative to the principal transitions could be accurately measured; two of these were sufficiently resolved for full scalar analyses. These frequencies were combined with results of several high-resolution Raman studies by other authors to yield the most complete data set on SF₆ vibrational levels yet obtained. Isotopic frequency shifts have also been measured. The effective Coriolis constants for combination and overtone bands of octahedral molecules are discussed.     

Time-resolved resonance raman spectra and decay kinetics of triplet anthracene in fluid media

Reported here are the time-resolved resonance Raman spectra and decay kinetics of the lowest triplet state (³B_2u⁺) of anthracene-h₁₀ and anthracene-d₁₀ molecules in fluid media at room temperature. The triplet population (≈3 × 10^?5 M) is observed to decay at microsecond times by triplet—triplet annihilation. Vibrational assignments for the observed Raman bands are proposed.     

Einkristall-Raman-Spektren von Alaunen. II. [1]. Raman-aktive Gitterschwingungen und FIR-Spektren

Single-Crystal Raman Spectra of Alums. II. Raman-active Lattice Vibrations and F.I.R. Spectra FIR and single crystal Raman spectra of seven different alums have been measured. All observed peaks are assigned to the symmetry species of the factor group T_h. A part of the lattice modes could be assigned to translational and rotational motions of the sulfate (selenate) sublattice and to motions of the crystal water – [Me^I(H₂O)₆]⁺ and [Me^III(H₂O)₆]³⁺ respectively. Comparison of spectra taken at 295 K and 80 K shows no frequency shifts significant for phase transition but a remarkable sharpening of especially those bands which are connected with water motions.     

Resonance raman scattering from metastable O2 molecules in γ-irradiated NaClO3

Resonance Raman scattering has been observed from metastable O₂ molecules produced in single crystals of NaClO₃ by γ-irradiation at 300 K. Evidence that the observed bands are due to O₂ is provided by the Raman spectrum of irradiated ¹⁸O enriched NaClO₃ in which bands due to ¹⁶O₂, ¹⁶O ¹⁸O, and ¹⁸O₂ were identified. The Raman band at 1544 cm^?1 ascribed to metastable O₂ disappears on bleaching with intense 4880 Å radiation enabling the identification of a weaker band at 1557 cm^?1 that is assigned to the stable form of O₂.     

A Raman and infrared spectroscopic study of the phosphate mineral laueite

A laueite mineral sample from Lavra Da Ilha, Minas Gerais, Brazil has been studied by vibrational spectroscopy and scanning electron microscopy with EDX. Chemical formula calculated on the basis of semi-quantitative chemical analysis can be expressed as (Mn²⁺_0.85,Fe²⁺_0.10Mg_0.05)_∑1.00(Fe³⁺_1.90,Al_0.10)_∑2.00(PO₄)₂(OH)₂·8H₂O.The laueite structure is based on an infinite chains of vertex-linked oxygen octahedra, with Fe³⁺ occupying the octahedral centers, the chain oriented parallel to the c-axis and linked by PO₄ groups. Consequentially not all phosphate units are identical. Two intense Raman bands observed at 980 and 1045 cm⁻¹ are assigned to the ν₁ PO₄³⁻ symmetric stretching mode. Intense Raman bands are observed at 525 and 551 cm⁻¹ with a shoulder at 542 cm⁻¹ are assigned to the ν₄ out of plane bending modes of the PO₄³⁻. The observation of multiple bands supports the concept of non-equivalent phosphate units in the structure. Intense Raman bands are observed at 3379 and 3478 cm⁻¹ and are attributed to the OH stretching vibrations of the hydroxyl units. Intense broad infrared bands are observed. Vibrational spectroscopy enables subtle details of the molecular structure of laueite to be determined.     

Raman,spectra of matrix-isolated lead molecules

Raman spectra of lead molecules in low-temperature rare-gas matrices show that dimers and larger clusters are isolated. Besides 7 “normal” Raman bands, two strong resonance progressions are found with frequencies of 108.5 and 118.5 cm^?1 in Xe and 111 and 119 cm^?1 in Kr. The 110 cm^?1 peak is assigned to Pb₂, close to the frequency for the X-O⁺_g state of gaseous Pb₂.