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.     

Magnetic circular dichroism of Eu(C2H5SO4)3·9H2O due to magnetic dipole transitions

The magnetic circular dichroism (MCD) for the three low-energy absorption bands of the Eu(C₂H₅SO₄)₃·9H₂O crystal has been measured at room temperature. It may be well understood from the MCD as well as from other experimental results that two of these bands, ⁷F₁ → ⁵D₀ and ⁷F₀ → ⁵D₁, are of magnetic dipole origin. However, the MCD of another band at about 18650 cm^?1, ⁷F₁ → ⁵D₁, cannot be interpreted as being only one electric dipole in origin, which has been pointed out by several investigations. The present MCD analysis indicates that although this broad band consists of one electric- and two magnetic-dipole transitions, each of which has a sizeable absorption strength, the MCD spectrum originates exclusively from the two magnetic dipole transitions     

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.     

On the structure, infrared and Raman spectra of the 2:1 cysteine–Zn complex

A recent study on the Raman spectrum of the cysteine zwitterion and anion, and the 2:1 (Cys)₂Zn complex was reanalyzed employing B3LYP/6-311++G(3df,2pd) calculations in a simulated water environment. The spectra were rediscussed in light of the apparent incorrect structure determined in the original paper for this complex. The complex turns out to be tetrahedral and tetracoordinated instead of octahedral hexacoordinated, as initially proposed. The calculated Raman spectrum of the complex agrees very well with the experimental data, showing that both the geometrical and electronic structures are well represented. Three metal–ligand bands are found, two of them involving mostly the symmetrical and asymmetrical stretching of the Zn–N and Zn–S bonds. They were measured at 334 and 296 cm^?1 and calculated at 319 and 249 cm^?1, respectively. The third band involves the stretching of Zn–S bonds but also skeletal vibrations of the ligand. This band, measured at 399 cm^?1 and calculated at 444 cm^?1, has been previously assigned incorrectly to a Zn–O bond which does not actually exists since the CO ₂ ^?1 fragments are located away from the Zn ion.     

Raman Combinations and Stretching Overtones from Water, Heavy Water, and NaCl in Water at Shifts to ca. 7000 cm−1

Photographic Raman spectra were obtained at shifts to ca. 7000 cm^–1 for pure water and for a saturated aqueous solution of NaCl using argon ion laser excitation. Raman spectra were also obtained photoelectrically for H₂O and D₂O between ca. 2500 and ca. 7000 cm^–1 using 248-nm excimer laser excitation and boxcar detection. Overtone and combination assignments are presented for H₂O and D₂O. The first IR OH-stretching overtone from water occurs 215 cm^–1 above the first Raman OH-stretching overtone because the IR overtones are dominated by asymmetric stretching. The second OH-stretching Raman overtone from water is estimated to occur near 10,020 ± 20 cm^–1, with 9950 cm^–1 as a lower limit.     

4-Hydroxycoumarin/2-hydroxychromone tautomerism: Infrared spectra of 2-13c and 3-D labeled 4-hydroxycoumarin and its anion

Bands with primarily v (C=O) and v (C=O) character in the spectra of 4-hydroxycoumarin and its anion were identified by isotopic substitution with either ¹³C or deuterium. Two bands of each type were found for spectra of 4-hydroxycoumarin in solution in chloroform, dioxane, or dimethylsulfoxide, with v (C=O) at 1704–1733 cm^?1 and ～ 1567 cm^?1. Two bands, at 1618 and 1559 cm^?1, are associated with v (C=C) in the spectrum of crystalline 4-hydroxycoumarin monohydrate, but only a single v (C=O) band at ～ 1655 cm^?1 was observed. Anhydrous 4-hydroxycoumarin has v (C=O) bands at ～ 1700 cm^?1 and a shoulder at ～ 1670 cm^?1. The strong band at 1660 cm^?1 in the spectrum of 4-hydroxycommarin anion in dimethylsulfoxide solution is due to a delocalized v (O = C = O) vibration, whereas the band at 1555 cm^?1 has partial v (C=C) character and involves C(3) but not C(2), supporting a fully delocalized char structure for the anion. No evidence for the existence of the 2-hydroxychromone tautomer was found, except in the case of anhydrous 4-hydroxycoumarin in the solid state.     

Infrared spectrum of D2O vibrationally decoupled in H2O ice Ic

The study of D₂O isolated in amorphous H₂O (ice Iv) has been extended to the determination of the bending mode frequency (1230 cm^?1) and to the measurement of the vibrational spectrum of the cubic ice phase (ice Ic). The vibrationally decoupled stretching frequencies (ν₁ = 2367 cm^?1 and ν₃ = 2444 cm^?1) for D₂O in the H₂O (Ic) have been obtained and an estimate of the exchange activation energy is given.     

FOURIER TRANSFORM INFRARED SPECTRAL STUDIES ON THE SCHIFF BASE MODE OF ALL-trans BACTERIORHODOPSIN and ITS PHOTOINTERMEDIATES,K and L*

Abstract– Difference Fourier transform infrared spectra were recorded for bacteriorhodopsin upon irradiation at 230, 170 or 77 K, which gave, respectively, the spectrum of the M, L or K intermediate minus unphotolyzed all-trans bacteriorhodopsin (denoted as BR). By replacement of the Schiff base nitrogen with ¹⁵N, or of either its hydrogen at N or C₁₅ with deuterium, the vibrational bands related to the Schiff base were identified and the isotope-shifts evaluated for BR, K and L. The 1348 cm^?l band of BR and K and the 1400 cm^?1 band of L were sensitive to each of these isotope substitutions. The 1254 cm^?1 band of BR, the 1245 cm^?1 band of K and the 1301 cm^?1 band of L were sensitive to either N- or C₁₅-deuteration but not to ¹⁵N-substitution. The N—D in-plane bending vibration of K and L appeared at 969 and 997 cm^?1, respectively, upon substitution with D₂O. All the results show that L is larger in frequencies related to the N—H in-plane bending vibration than K or BR and suggest that L has the strongest interaction with the protein. Among the bands containing an N—H bending vibration, the 1348 cm^?1 band of K was more intense than the corresponding band of L at 1400 cm^?1. The C₁₅-deuteration-induced upshift of the 1245 cm^?1 band of K was unobservable for the 1301 cm^?1 band of L. Such differences between L and K might be brought about by a distortion in the retinal moiety close to the protonated Schiff base of the 13-cis chromophore.     

RESONANCE RAMAN SPECTRUM OF THE EXCITED 21Ag STATE OF ß-CAROTENE

Abstract— Resonance Raman (RR) bands assignable to the 2¹A_g excited state of ß-carotene are recorded using picosecond time-resolved resonance Raman (PTR³) spectroscopy. The RR spectrum contains bands in both the C-C (1204 cm^?1, 1243 cm^?1, and 1282 cm^?1) and C=C (1777 cm^?1) stretching regions. The time-dependent intensities of these RR features, measured with ? 30 ps. resolution, are found (i) to closely correlate with picosecond transient absorption (PTA) data recorded at 575 nm on the same sample and (ii) inversely correlate with the time-dependent intensities of RR bands assigned to the 1¹A_g ground state. Both of these observations support the assignment of these four RR features to the 2¹A_g excited state. These results remove uncertainties associated with earlier experiments in which excited-state RR scattering from (3-carotene was not observed in spite of predicted trends emanating from studies of shorter polyene compounds. The observed C=C band position also agrees with a recent report of this feature.     

Electronic transitions in Li4CoCl4.10H2O

The electronic spectrum of Li₄CoCl₆.10H₂O was recorded at liquid nitrogen temperature in the 4,000–25,000 cm^?1 spectral region. The simi larity of this spectrum to that of CoCl₂ permitted us to assume O_h syn metry of the [CoCl₆]^4? cluster in our sample. The band assignment was performed in the crystal field approximation using Tanabe and Sugano's energy matrices for Dq = 730 cm^?1, B = 820 cm^?1 and C/B = 4.4.The large number of bands and high intensity of the maxima in the regio 19,000–21,000 cm^?1 is discussed.     

IR and Raman Vibrational Assignments for Metal-free Phthalocyanine from Density Functional B3LYP／6-31G（d） Method

Vibrational (IR and Raman) spectra for the metal-free phthalocyanine (H2Pc) have been comparatively investigated through experimental and theoretical methods. The frequencies and intensities were calculated at density functional B3LYP level using the 6-3 IG(d) basis set. The calculated vibrational frequencies were scaled by the factor 0.9613 and compared with the experimental result. In the IR spectrum, the characteristic IR band at 1008.cm^-1 is interpreted as C-N (pyrrole) in-plane bending vibration, in contrast with the traditional assigned N-H in-plane or out-of-plane bending vibration. The band at 874 cm^-1 is attributed to the isoindole deformation and aza vibration. In the Raman spectrum, the bands at 540, 566, 1310, 1340, 1425, 1448 and 1618 cm^-1 are also re-interpreted. Assignments of vibrational bands in the IR and Raman spectra are given based on density functional calculations for the first time. The present work provides valuable information to the traditional empirical assignment and will be helpful for further investigation of the vibration spectra of phthalocyanine analogues and their metal complexes.     

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.     

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.     

Infrared and Raman spectroscopic characterization of the phosphate mineral kosnarite KZr2(PO4)3 in comparison with other pegmatitic phosphates

In this research, we have used vibrational spectroscopy to study the phosphate mineral kosnarite KZr₂(PO₄)₃. Interest in this mineral rests with the ability of zirconium phosphates (ZP) to lock in radioactive elements. ZP have the capacity to concentrate and immobilize the actinide fraction of radioactive phases in homogeneous zirconium phosphate phases. The Raman spectrum of kosnarite is characterized by a very intense band at 1,026?cm^?1 assigned to the symmetric stretching vibration of the PO₄ ^3? ??₁ symmetric stretching vibration. The series of bands at 561, 595 and 638?cm^?1 are assigned to the ??₄ out-of-plane bending modes of the PO₄ ^3? units. The intense band at 437?cm^?1 with other bands of lower wavenumber at 387, 405 and 421?cm^?1 is assigned to the ??₂ in-plane bending modes of the PO₄ ^3? units. The number of bands in the antisymmetric stretching region supports the concept that the symmetry of the phosphate anion in the kosnarite structure is preserved. The width of the infrared spectral profile and its complexity in contrast to the well-resolved Raman spectrum show that the pegmatitic phosphates are better studied with Raman spectroscopy.     

A study of helix formation in polydimethysiloxane by Raman scattering

Depolarization ratios ρ of the Raman bands due to CH₃ stretching at 2907 cm^?1 and the Si? O skeletal mode at 491 cm^?1 have been measured in polydimethylsiloxane gum as a function of temperature from 100°C to ?45°C. Below 0°C the changes in p have been interpreted in terms of the formation of helical regions in the gum. The enthalpy of helix formation ΔH has been determined as 3200 ± 600 cal/mole. An upper limit on the entropy change, ΔS, of 16 ± 3 e.u./mole and minimum values of helix content at different temperatures have been found. The Raman spectrum of crystalline polydimethylsiloxane is presented.     

Raman and Photoluminescence Spectroscopic Detection of Surface‐Bound Li+O2− Defect Sites in Li‐Doped ZnO Nanocrystals Derived from Molecular Precursors

We present a detailed study of Raman spectroscopy and photoluminescence measurements on Li‐doped ZnO nanocrystals with varying lithium concentrations. The samples were prepared starting from molecular precursors at low temperature. The Raman spectra revealed several sharp lines in the range of 100–200 cm^?1, which are attributed to acoustical phonons. In the high‐energy range two peaks were observed at 735 cm^?1 and 1090 cm^?1. Excitation‐dependent Raman spectroscopy of the 1090 cm^?1 mode revealed resonance enhancement at excitation energies around 2.2 eV. This energy coincides with an emission band in the photoluminescence spectra. The emission is attributed to the deep lithium acceptor and intrinsic point defects such as oxygen vacancies. Based on the combined Raman and PL results, we introduce a model of surface‐bound LiO₂ defect sites, that is, the presence of Li⁺O₂^? superoxide. Accordingly, the observed Raman peaks at 735 cm^?1 and 1090 cm^?1 are assigned to Li? O and O? O vibrations of LiO₂.     

Local Raman tensors in adenosine triphosphoric acid

A polarized laser (488.0 nm) Raman spectroscopic measurement has been made on a single crystal of a disodium salt of adenosine triphosphoric acid (Na₂ATP·3H₂O) by the use of a Raman microscope. The crystal belongs to an orthorhombic system of the space group P2₁2₁2₁, and has dimensions of 10, 100 and 100 μm along the crystallographic axes a, b and c, respectively. For each Raman band in the 300–1800 cm⁻¹ range, the scattering intensity ratio I _bb/I _cc of the bb and cc polarization components has been determined. For a few bands, the relative intensities of the bc components were also estimated. To augment the data, the depolarization ratio of each Raman band of ATP has also been determined for its acidic (pH = 2.42) H₂O and D₂O solutions. From these experimental results, the shapes and orientations of the Raman scattering tensors which are considered to be localized in the adenine-H⁺ portion and in the phosphate portion of the molecule have been derived.     

Coordination of cations in TiNb2O7 by Raman spectroscopy

The Raman spectrum of the compound TiNb₂O₇ prepared by a liquid mix technique was recorded at room temperature using the 530.98-nm line from a krypton-ion laser as exciter. The bands observed at 998 and 884 cm^?1 are assigned to the edge-shared and corner-shared NbO₆ octahedra, respectively. The relative intensities of these two bands are consistent with the structure of TiNb₂O₇ worked out by earlier investigators using X-ray and neutron diffraction. The strong band observed at 647 cm^?1 is assigned to the vibration of the TiO₆ octahedra. The octahedral coordination for both cations based on the results of the Raman spectrum measurements is in essential agreement with the available structural data for the compound TiNb₂O₇. The weak band observed at 840 cm^?1 is suggestive of the presence of NbO₄ tetrahedra in small concentrations in TiNb₂O₇.     

Fourier transform infrared spectroscopic analyses of the v12 fundamentals of C2H4 and C2D4

High-resolution infrared studies of isotopic ethylenes below 2000 cm^?1 have been commenced with a Nicolet FTIR spectrometer. Accurate vibration and rotation parameters for the v₁₂ fundamentals of C₂H₄ and C₂D₄ are determined from spectra recorded with 0.05 cm^?1 resolution. Excellent band contour simulations confirm that these bands are unperturbed throughout their range.     

Vibrational spectra of hypophosphite ion and its deuterated species

The infrared and Raman spectra of the H₂PO₂^?, HDPO₂^? and D₂PO₂^? ions have been measured in aqueous solutions. The assignment of bands to the fundamental vibrations proposed is based on experimental tests, band polarisation measurements, application of all known isotopic rules and the construction and analysis of all the physically admissible assignments. The thermodynamic functions of the studied ions are calculated in the rigid rotator and harmonic vibrator approximation.