Fourier transform Raman spectroscopy of Syncrude Sweet Blend distillation fractions: the 200-1800 cm-1 region

The fingerprint (200-1800 cm(-1)) region in FT-Raman spectra of Syncrude Sweet Blend (SSB) and its three constituent distillation fractions (naphtha, light gas oil and heavy gas oil) was analyzed in detail in this study. Approximately 50 bands were observed and assigned to functional groups in saturated (alkanes) and unsaturated (aromatics) species. Characteristic bands for mono-, bi-, and tricyclic aromatics were identified and used to quantify these groups in SSB and the distillation fractions. Total aromatics content was determined using the carbon-carbon stretching bands in the 1600-cm(-1) region, and shown to agree with earlier results obtained from the C-H stretching region. The bands due to mono- and bicyclic aromatics permitted calculation of the relative abundances of these species with an accuracy equivalent to that obtained using NMR spectroscopy, a traditional method for measuring this quantity.     

Fourier transform Raman spectroscopy of Syncrude sweet blend distillation fractions derived from Athabasca bitumen

The C-H stretching region in FT-Raman spectra of Syncrude sweet blend (SSB) and three distillation fractions (naphtha, light gas oil and heavy gas oil) was analyzed in detail in this investigation. The frequencies and intensities of the 11 aliphatic and three aromatic C-H bands used to fit the spectrum of SSB were equal to the averages (weighted sums) of the corresponding quantities in the spectra of the fractions. The additivity of the spectra, thought to be a consequence of the large number of discrete compounds contained in each fraction, makes it possible to estimate the composition of other SSB samples using the spectra of the fractions reported in this work. In the aromatic C-H region, total intensities can be used to calculate the distribution of aromatics among the distillation fractions; these data also permit calculation of the fractional aromaticity (per cent aromatic carbon) for SSB and each fraction, with accuracies comparable to those obtained using NMR spectroscopy.     

FT-Raman and photoacoustic infrared spectroscopy of Syncrude heavy gas oil distillation fractions

FT-Raman and photoacoustic (PA) infrared spectra of six distillation fractions derived from Syncrude heavy gas oil (HGO), which has a boiling range from 343 to 524 degrees C, were analyzed in detail in this study. Most of the information on the fingerprint region (200-1,800 cm(-1)) is provided by the FT-Raman spectra, which display approximately 30 bands that are assignable to functional groups in alkanes or aromatics. Monocyclic, bicyclic and tricyclic aromatics in the six fractions were also monitored using bands in this region. The C-H stretching region in both the FT-Raman and PA infrared spectra of the HGO distillation fractions was analyzed according to a curve-fitting algorithm used in previous investigations of samples with lower boiling points. The PA spectra of the HGO fractions were also analyzed by integration. The curve-fitting results show that the frequencies of the 11 Raman and 8 infrared bands used to model the aliphatic (approximately 2,775-3,000 cm(-1)) parts of the respective spectra are approximately constant across the entire HGO boiling range. These band positions are consistent with the results obtained in earlier studies of other distillation fractions obtained from Syncrude sweet blend. Both curve-fitting and integration show that the respective proportions of CH(2) and CH(3) groups do not vary significantly within the HGO region.     

Resonance Raman spectra of n-methylthioacetamide

Rigorous resonance, as well as preresonance Raman spectra of N-methylthioacetamide and its N-deuterated compound are reported. The observed selectivity in the resonance intensity enhancement is discussed in relation to the potential energy distributions obtained by normal coordinate treatment. The structural change concerning the CN and CS bond lengths is suggested to accompany the π^* ← π electronic excitation.     

The Raman spectra of bromoform

In this work the Raman spectrum of bromoform is recorded at various temperatures in the pure compound and in solution in carbon tetrachloride and the features shown by some of the bands are considered in the light of previous spectroscopic data interpretations. In particular, the concentration dependent effects exhibited by the ν₅(e) vibrational mode suggest, by comparison with similar effects previously observed in chloroform and trichloromethyl fluoride, the existence, in the pure liquid at room temperature, of important intermolecular interactions.     

Raman spectra of some terpenes

Summary Investigation of Raman spectra indicates increase in the interaction between the double bonds as we pass from sylvestrene and isosylvestrene to sylveterpinolene and indicates that the character of the interaction in the last compound is more complex than in 1,3-butadiene and other similar conjugated systems.     

Raman spectra of inorganic ions

This paper contains the Raman spectra of 79 inorganic salts and sulphur which may be used as an aid in qualitative inorganic analyses. These were obtained some years ago by conventional Raman spectroscopy. No such collection exists and the order of the reference spectra is identical to those in a collection of IR spectra. A table of characteristic frequencies for 17 polyatomic ions is given. These data have increased relevance following the emergence of FT-Raman as a rapid and efficient modern technique.     

Raman spectra of titanium dioxide

First-order Raman spectra have been recorded at room temperature for the anatase and rutile phases of polycrystalline titanium dioxide using an argon ion laser as exciter. The high-temperature rutile phase was found to be stabilized at temperatures below 450°C. Anatase transforms to rutile phase at ～750°C. All the Raman active fundamentals predicted by group theory are observed.     

Raman spectra of chlorophyll forms

The Raman spectra of chlorophyll a (Chl) forms in aqueous poly(vinyl alcohol) (PVA) and in dimethyl sulfoxide (DMSO)—water mixtures were recorded at 457.9 nm excitation and their structures were characterized by comparison with the spectra of the following well-known chlorophyll forms: (1) monomers (Chl)₁ in the polar solvents of group (A), i.e., diethyl ether, tetrahydrofuran, acetone, N,N-dimethylformamide and DMSO, of which the oxygen atom is expected to coordinate to the central magnesium atom; (2) monomers (Chl)₁ in the polar solvents of group (B), i.e., methanol, ethanol, 1-propanol, 2-propanol and 1-butanol, which are supposed to form a hydrogen-bond to the C₉=O group in addition to the coordination-bond to the Mg atom; (3) dehydrated aggregates (Chl)_n in dry non-polar solvents, i.e., carbon tetrachloride, n-hexane and n-octane; and (4) hydrated aggregates (Chl·2H₂O)_n in wet non-polar solvents, i.e., n-hexane and n-octane. The frequency of the C₉ = O stretching Raman line of each of the above chlorophyll forms was: (1) 1702—1680 cm⁻¹; (2) 1673—1668 cm⁻¹; (3) around 1655 cm⁻¹; (4) around 1645 cm⁻¹. The frequency proved to be a marker of intermolecular interaction of the Chl molecules. The spectral patterns in the 1650—700 cm⁻¹ region of (1), (2) and (3) were similar. However, the relative intensities of Raman lines of (4), which was ascribed to a one-dimensional, regular stacking of the Chl macrocycles, were quite different from those of (1)—(3).The chlorophyll form in PVA aqueous solution was identified as (Chl·2H₂O)_n by spectral comparison. The chlorophyll forms present in the DMSO—water mixtures were highly dependent on the DMSO content. It is suggested that (Chl)₁ having hydrogen-bonded H₂O should be present in 10% DMSO solution, and that a new chlorophyll form (Chl·DMSO)_n having (a) a stoichiometric intermolecular interaction with DMSO and (b) a regular stacking of the chlorophyll macrocycles, should be predominant in 50% DMSO aqueous solution.     

Raman spectra of carotenoids in natural products

Resonance Raman spectra of naturally occurring carotenoids have been obtained from nautilus, periwinkle (Littorina littorea) and clam shells under 514.5 nm excitation and these spectra are compared with the resonance Raman spectra obtained in situ from tomatoes, carrots, red peppers and saffron. The tomatoes, carrots and red peppers gave rise to resonance Raman spectra exhibiting a nu1 band at ca. 1520 cm(-1), in keeping with its assignment to carotenoids with ca. nine conjugated carbon-carbon double bonds in their main chains, whereas the resonance Raman spectrum of saffron showed a nu1 band at 1537 cm(-1) which can be assigned to crocetin, having seven conjugated carbon-carbon double bonds. A correlation between nu1 wavenumber location and effective conjugated chain length has been used to interpret the data obtained from the shells, and the wavenumber position (1522 cm(-1)) of the nu1 band of the carotenoid in the orange clam shell suggests that it contains nine conjugated double bonds in the main chain. However, the black periwinkle and nautilus shells exhibit nu1 bands at 1504 and 1496 cm(-1), respectively. On the basis of the correlation between nu1 wavenumber location and effective conjugated chain length, this indicates that they contain carotenoids with longer conjugated chains, the former having ca. 11 double bonds and the latter ca. 13 or even more. Raman spectra of the nautilus, periwinkle and clam shells also exhibited a strong band at 1085 cm(-1) and a doublet with components at 701 and 705 cm(-1), which can be assigned to biogenic calcium carbonate in the aragonite crystallographic form.     

X—射线荧光光谱测定甜饮料中微量元素

本文提出了低温蒸干和炭化制样Ｘ－射线荧光分析甜饮料中１６种微量元素的方法，试样在电热板上经低温蒸干，于马旨炉中３００℃炭化３０ｍｉｎ，在液压样品成形机上压制成样片进行测定，所测元素不需用任何基体校正，由微机从校正曲线查得含量，榈分析结果与ＩＣＰ－ＡＥＳ和ＡＡＳ法相吻合。     

The Raman spectra of the cylophanes

Raman spectra have been obtained for the entire series of [2_n]-cyclophanes and along with the i.r. spectra, several band assignments have been proposed. A correlation of the frequencies of the in-plane ring modes of the cyclophane with those of the identically substituted methylated benzene has been made. The CH₂ stretching bands have been found to move to higher frequency as the degree of steric hindrance increased. Tentative assignments have been proposed for the aromatic CH out-of-plane wag, and a possible origin for the distorted benzene band is discussed.     

Raman spectra of ordered crystalline ethane

The Raman spectrum of ethane in phase II at 74 K has been obtained. The spectrum lends support to the crystal structure previously deducted from i.r. spectra.     

Raman spectra of diglycine selenate crystals

A detailed symmetry analysis of the vibrational modes of a new diglycine selenate crystal (DGSe) by the group-theoretical method is given. Raman spectra of DGSe were recorded at 78 K, and the observed lines were assigned to the characteristic vibrations of SeO₄, CH₂, NH₂, COO and CN groups.     

Raman spectra of overheated sulfur vapor

Our thermodynamic study allows to confirm the selective observation with a blue exciting line (457.9 or 476.5 nm) of the resonance Raman spectra of the S₃ molecule. The extinction coefficient of the maximum λ = 395 nm of its absorption spectrum ε = 2100 1 mole⁻¹ cm⁻¹ is quite lower than that previously reported. The resonance Raman spectra of ³²S₃ and ³⁴S₄ may be explained with three normal frequencies and confirm the bent C_2v geometry of this molecule in perfect agreement with the structure of the parent anions, S⁻₃ and S²⁻₃.     

罗丹明6G的荧光光谱

在苯-甲醇混合溶剂中测量了罗丹明6G的吸收光谱和荧光光谱,发现体系中荧光强度和光密度随甲醇浓度的增长而增长.这可解释为甲醇浓度增加,溶液的介电常数也增加,这样自由离子浓度增加,未解离分子浓度减少.结果表明无论由吸收光谱和由荧光光谱都说明荧光来源于R6G离子.