Near-infrared combination and overtone bands of CH in CHX3, CHX(2)-CHX2, and CHX(2)-CX(2)-CHX2

In the present report we studied spectral characteristics of the near-infrared combination and overtone bands of CH vibrations of a CH sequence. The near-infrared bands of the CH in CHX3 (X, halogen), which were interpreted in terms of the CH stretching and CH deformation fundamentals without any ambiguity, typically showed how the frequency and intensity of a combination or an overtone depend on the vibrational excited state. In the CH-C-CH of CHX2CX2CHX2, the vibrations of one CH are isolated from those of the other CH, and the combination and overtone bands were similarly interpreted as those of the CH, although each of the combination bands was split into two because of non-degeneracy of the CH deformation. In the CH-CH of CHX2CHX2, the CH deformations only have coupled modes. The first combination showed four narrowly separate bands, which were reasonably interpreted on the basis of the CH stretching and the coupled CH deformation modes. We demonstrated that the first combination of coupled modes as well as the combination of up to, at least, the third order of isolated modes have the nature of the characteristic bands.     

Short-wavelength near-infrared spectra of sucrose, glucose, and fructose with respect to sugar concentration and temperature

Short-wavelength near-infrared (SW-NIR) (700-1100 nm) spectra of aqueous solutions of sucrose, D-glucose, and D-fructose were monitored with respect to change in temperature and sugar concentration. Sugar OH and CH related vibrations were identified by analysis of the spectra of sugar solutions in deuterium oxide (D2O), and of sucrose-d8 solutions in D2O. Absorption spectra were explained in terms of the second and third overtones of OH stretching vibrations and the third overtone of CH2 and CH stretchings. In deuterated solutions, CH and CH2 higher overtone vibration bands became apparent. The major spectral effect of decreased temperature or increased sugar concentration was a decrease in absorbance at 960 nm and an increase in absorbance at 984 nm, interpreted as an increase in the degree of H bonding. Partial least-squares (PLS) calibrations on sugar concentrations (with spectra collected at several sample temperatures) relied strongly on the 910 nm sugar CH related bands, whereas calibrations on temperature depended equally on all OH associated vibrations (750, 840, 960, and 985 nm).     

Strong overtones and combination bands in ultraviolet resonance Raman spectroscopy

Ultraviolet resonance Raman spectroscopy is carried out using a continuous wave frequency-doubled argon ion laser operated at 229, 244, and 257 nm in order to characterize the overtones and combination bands for several classes of organic compounds in liquid solutions. Contrary to what is generally anticipated, for molecules such as pyrene and anthracene, strong overtones and combination bands can show up; it is demonstrated that their intensity depends critically on the applied laser wavelength. If the excitation wavelength corresponds with a purely electronic transition--this applies to a good approximation for 244-nm excitation in the case of pyrene and for 257-nm excitation in the case of anthracene--mostly fundamental vibrations (up to 1700 cm(-1)) are observed. Overtones and combination bands are detected but are rather weak. However, if the laser overlaps with the vibronic region--as holds for 229- and 257-nm excitation for pyrene and 244-nm excitation for anthracene--very strong bands are found in the region 1700-3400 cm(-1). As illustrated for pyrene at 257 nm, all these bands can be assigned to first overtones or binary combinations of fundamental vibrations. Their intensity distribution can roughly be simulated by multiplying the relative intensities of the fundamental bands. Significant bands can also be found in the region 3400-5000 cm(-1), corresponding with second overtones and ternary combinations. It is shown that these findings are not restricted to planar and rigid molecules with high symmetry. Substituted pyrenes exhibit similar effects, and relatively strong overtones are also observed for adenosine monophosphate and for abietic acid. The reasons for these observations are discussed, as well as the potential applicability for analytical purposes.     

Radiative, collisional, and predissociative effects in CH laser-induced-fluorescence flame thermometry

Laser-induced fluorescence of the CH radical is used to determine the flame-front temperature of an 8-Torr premixed CH(4)/O(2) flame. The A (2)D-X (2)Delta (0, 0) and B (2)Sigma- - X (2)II (0, 0) bands give values of 1960 +/- 60 and 1920 +/- 70 K, respectively. This is an improvement over a previous study that found discrepancies up to 20% between these bands. New rotational-level-dependent transition probabilities are the main reason for this improvement. The weaker off-diagonal bands A-X (0, 1) and B-X (0, 1) yield temperatures of 1930 +/- 90 and 1830 +/- 100 K, respectively. The influence of rotational transfer on the predissociated levels that have N' > in B (2)Sigma-, v'= 0 was investigated with fluorescence scans and a statistical power-gap law model of the relaxation; deviations up to 8% in temperature can occur because of this process.     

Absorption measurement of nu2 + 2nu3 band of CH4 at 1.33 microm using an InGaAsP light emitting diode

The combination band of nu2 + 2nu3 of CH4 at 1.33 microm (7512 cm(-1)) was observed at 0.3-cm(-1) resolution by a simple experimental arrangement using a near-infrared high-radiant InGaAsP light emitting diode (LED) and a Ge detector. Forty-six line centers were measured with accuracies of 0.03 cm(-1). The assignment of these manifolds was made by inspection of the P, Q, and R branches. The experimental result indicates that the nu2 + 2nu3 band can be used for fully optical remote monitoring of methane using InGaAsP optical sources in conjunction with an ultralow-loss optical fiber network.     

Atmospheric CH4 and H2O monitoring with near-infrared InGaAs laser diodes by the SDLA, a balloonborne spectrometer for tropospheric and stratospheric in situ measurements

The Spectromètre à Diodes Laser Accordables (SDLA), a balloonborne spectrometer devoted to the in situ measurement of CH(4) and H(2)O in the atmosphere that uses commercial distributed-feedback InGaAs laser diodes in combination with differential absorption spectroscopy, is described. Absorption spectra of CH(4) (in the 1.653-mum region) and H(2)O (in the 1.393-mum region) are simultaneously sampled at 1-s intervals by coupling with optical fibers of two near-infrared laser diodes to a Herriott multipass cell open to the atmosphere. Spectra of methane and water vapor in an altitude range of ~1 to ~31 km recorded during the recent balloon flights of the SDLA are presented. Mixing ratios with a precision error ranging from 5% to 10% are retrieved from the atmospheric spectra by a nonlinear least-squares fit to the spectral line shape in conjunction with in situ simultaneous pressure and temperature measurements.     

Overtones and combinations in single-molecule surface-enhanced resonance Raman scattering spectra

The observation of overtones and combinations in the SERRS spectra of single molecules dispersed in Langmuir-Blodgett monolayers is confirmed for a family of molecules. The detection of fundamentals, combinations, and overtones in single-molecule spectra of a series of perylenetetracarboxylic diimides (PTCD) is achieved with spatially resolved surface-enhanced resonance Raman scattering (SERRS). The Langmuir-Blodgett technique is used to create monomolecular thick films on metal islands containing on average one probed molecule within the field of view of the Raman microscope. The enhancement needed for single-molecule detection is achieved through the multiplicative effects of electromagnetic enhancement by metal nanostructures and resonance Raman enhancement by excitation into molecular electronic absorption bands. Overtone and combination progressions are well resolved in the average SERRS spectra of all three PTCD molecules.     

Characterisation of bauxite and seawater neutralised bauxite residue using XRD and vibrational spectroscopic techniques

Bauxite refinery residues are derived from the Bayer process by the digestion of crushed bauxite in concentrated caustic at elevated temperatures. Chemically, it comprises, in varying amounts (depending upon the composition of the starting bauxite), oxides of iron and titanium, residual alumina, sodalite, silica, and minor quantities of other metal oxides. Bauxite residues are being neutralised by seawater in recent years to reduce the alkalinity in bauxite residue, through the precipitation of hydrotalcite-like compounds and some other Mg, Ca, and Al hydroxide and carbonate minerals. A combination of X-ray diffraction (XRD) and vibrational spectroscopy techniques, including mid-infrared (IR), Raman, near-infrared (NIR), and UV–Visible, have been used to characterise bauxite residue and seawater neutralised bauxite residue. The ferric (Fe³⁺) ions within bauxite residue can be identified by their characteristic NIR bands, where ferric ions produce two strong absorption bands at 25,000 and 14,300 cm⁻¹. The presence of adsorbed carbonate and hydroxide anions can be identified at around 5,200 and 7,000 cm⁻¹, respectively, attributed to the 2nd overtone of the 1st fundamental overtones observed in the mid-IR spectra. The complex bands in the Raman and mid-IR spectra around 3,500 cm⁻¹ are assigned to the OH-stretching vibrations of the various oxides present in bauxite residue, and water. The combination of carbonate and hydroxyl units and their fundamental overtones give rise to many of the features of the NIR spectra.     

Measuring methane and its isotopes 12CH4, 13CH4, and CH3D on the surface of Mars with in situ laser spectroscopy

In light of the recent discovery of methane on Mars and its possible biological origin, a strategy is described for making in situ measurements of methane and its isotopes on the surface of Mars by laser spectroscopy in the 3.3-microm wavelength region. An instrument of reasonable mass (approximately 1 lb) and power (few watts) is capable of measuring mixing ratios down to 0.1 part per 10(9) by volume, a hundred times lower than recently reported observations. Making accurate measurements of 13CH4 and CH3D will be more difficult. For measuring delta13C to 10/1000 and deltaD to 50/1000, sample preconcentration will be required to approximately 3 parts per 10(6) by volume for delta13C and to approximately 40 parts per 10(6) by volume for deltaD. This need would be mitigated by the discovery of larger local abundances of methane near the source regions.     

High-precision continuous-flow measurement of delta13C and deltaD of atmospheric CH4

We describe our development of a CH4 preconcentration system for use with continuous-flow gas chromatograph combustion isotope ratio mass spectrometry (GC/C/IRMS). Precision of measurement of delta13C-CH4 is 0.05/1000 (1sigma) on multiple 60-mL aliquots of the same ambient air sample. The same front-end on-line CH4 preconcentration system allows us to measure deltaD of CH4 by gas chromatography IRMS when the combustion furnace is replaced with a pyrolysis oven (GC/P/IRMS). Precision of measurement for deltaD-CH4 is 1.5/1000 (1sigma) using 120 mL of ambient air based on multiple aliquots of the same air sample. These are the first reported measurements of atmospheric CH4 using GC/P/IRMS methodology. Each isotope analysis can be made much more rapidly (30-40 min) than they could using off-line combustion of an air sample (1-6 h) followed by conventional dual-inlet IRMS measurements (12-20 min), while requiring much less total volume and retaining a comparable level of precision and accuracy. To illustrate the capabilities of our preconcentration GC/C/IRMS system, we compare the results of measurement of 24 background air samples made using both GC/C/IRMS and conventional vacuum line/dual-inlet IRMS methodology. The air samples were collected on a shipboard air sampling transect made across the Pacific Ocean in July 2000 and are part of an ongoing atmospheric CH4 research program. The average difference between the two methods of IRMS analyses on these 24 samples is 0.01 +/- 0.03/1000 (95% confidence interval) for delta3C-CH4. These are the first measurements to be reported of air samples directly intercompared for delta13C-CH4 using both GC/C/IRMS and dual-inlet IRMS measurement methodology. Measurement of deltaD-CH4 of these air samples is also presented as an illustration of the ability of this system to resolve small isotopic differences in remote air. High-precision measurement of delta13C and deltaD of atmospheric CH4 made using our coupled preconcentration GC/IRMS system will greatly improve our ability to utilize isotopic data in understanding spatial and temporal changes in atmospheric CH4 and the biogeochemistry of its sources and sinks.     

Analytical evidence for the monolayer-protected cluster Au225[(S(CH2)5CH3)]75

The Brust synthesis of thiolate-protected gold clusters has been modified to produce identifiable proportions of a hexanethiolate-protected Au225 core nanoparticle that display quantized double layer charging voltammetry consistent with a Au225 core dimension. Transmission electron microscopy (TEM) and thermogravimetric results indicate an average nanoparticle formula of Au225[(S(CH2)5CH3)]75. A simulated pulse voltammogram that accounts for the TEM nanoparticle dispersity matches reasonably well with that of the polydisperse synthetic sample containing the Au225 component. In confirmation of the size determination, an HPLC analysis using ratiometric absorbance and electrochemical detectors gives a core radius of 1.0 nm for the Au225 nanoparticle.     

Near-infrared spectroscopy of H3+ above the barrier to linearity

Since the Royal Society Discussion Meeting on H3+ in 2000, the laboratory spectroscopy of H3+ has entered a new regime. For the first time, transitions of H3+ above the barrier to linearity have been observed. A highly sensitive near-infrared spectrometer based on a titanium:sapphire laser and incorporating a dual-beam, double-modulation technique with bidirectional optical multi-passing has been developed in order to detect these transitions, which are more than 4600 times weaker than the fundamental band. We discuss our recent work on the 2v1 + 2v2(2) <-- 0, 3v1 + v2(1) <-- 0, v1 + 4v2(2) <-- 0, v1 + 4V2(4) <-- 0 and 2v1 + 3v2(1) <-- 0 combination bands and the 5v2(1) <-- 0, 5v2(3) <-- 0, 52(5) <-- 0 and 6v2(2) <-- 0 overtone bands. Experimentally determined energy levels provide a critical test of ab initio calculations in this challenging energy regime (greater than 10,000 cm(-1)). By comparing the experimental energy levels and theoretical energy levels from ab initio calculations in which the adiabatic and relativistic corrections are incorporated, the extent of higher-order effects such as non-adiabatic and radiative corrections is revealed.     

Rapid, online quantification of H2S in JP-8 fuel reformate using near-infrared cavity-enhanced laser absorption spectroscopy

One of the key challenges in reforming military fuels for use with fuel cells is their high sulfur content, which can poison the fuel cell anodes. Sulfur-tolerant fuel reformers can convert this sulfur into H(2)S and then use a desulfurizing bed to remove it prior to the fuel cell. In order to optimize and verify this desulfurization process, a gas-phase sulfur analyzer is required to measure H(2)S at low concentrations (<1 ppm(v)) in the presence of other reforming gases (e.g., 25-30% H(2), 10-15% H(2)O, 15% CO, 5% CO(2), 35-40% N(2), and trace amounts of light hydrocarbons). In this work, we utilize near-infrared cavity-enhanced optical absorption spectroscopy (off-axis ICOS) to quantify H(2)S in a JP-8 fuel reformer product stream. The sensor provides rapid (2 s), highly precise (±0.1 ppm(v)) measurements of H(2)S in reformate gases over a wide dynamic range (0-1000 ppm(v)) with a low detection limit (3σ = ±0.09 ppm(v) in 1 s) and minimal cross-interferences from other present species. It simultaneously quantifies CO(2) (±0.2%), CH(4) (±150 ppm(v)), C(2)H(4) (±30 ppm(v)), and H(2)O (±300 ppm(v)) in the reformed gas for a better characterization of the fuel reforming process. Other potential applications of this technology include measurement of coal syngas and H(2)S in natural gas. By including additional near-infrared, distributive feedback diode lasers, the instrument can also be extended to other reformate species, including CO and H(2).     

Molecular design of copolymers based on polyfluorene derivatives for Bulk-heterojunction-type solar cells

Poly{[2,7-(9,9′-dihexylfluorene)]-alt-[4,7-di(thiophen-2-yl)benzo[c][1, 2, 5]thiadiazole]} (PFDTBT) with low band gap was reported as an intriguing and promising donor in Bulk-heterojunction-type solar cells. In this paper, based on the structure of PFDTBT, three new kinds of donor materials: poly{[2,7-(9,9′-dihexylfluorene)]-alt-[4,7-di(thiophen-2-yl)-[1, 2, 5]thiadiazolo[3,4-d]pyridazine]} (PFDTTDP), poly{[2,7-(9,9′-dihexyloxyfluorene)]-alt-[4,7-di(thiophen-2-yl)-[1, 2, 5]thiadiazolo[3,4-d]pyridazine]} (POFDTTDP), and poly{[2,6-(4,4-dihexyl)-4H-cyclopenta[2,1-b;3,4-b’]-dithiophene)-alt-[4-(1,3,4-thiadiazol-2-yl)-7-(thiophen-2-yl)-[1, 2, 5]thiadiazolo[3,4-d]pyridazine]} (PCPTTTDP), were designed and computed by density function theory (DFT). The electronic, optical and photovoltaic properties, and charge transport rates were investigated. The reorganization energies for holes and electrons are around 0.11 and 0.08 eV, respectively. It indicates that PFDTTDP, POFDTTDP, and PCPTTTDP are good candidates for donor material. Especially, when 6,6-phenyl-C61-butyric acid methyl ester (PC₆₁BM) functions as acceptor, PCPTTTDP has the most appropriate highest occupied molecular orbital and lowest unoccupied molecular orbital energy, and has the broadest absorption in the near-infrared region.     

[Ag(PPh_3)_2(CH_3COO)]_2·3H_2O的合成和晶体结构

将醋酸银和三苯基磷按1∶2摩尔比例进行反应得到化合物Ag(PPh3)2(CH3COO)]2,采用红外光谱、核磁共振、元素分析和单晶X射线衍射的方法,对其结构进行了表征.晶体结构解析结果显示,配合物属单斜晶系,空间群C2/c,a=44.286 8',b=13.269 6',c=24.997 0',α=90.000°,β=105.573°,γ=90.000°,Z=8,R=0.052 0,wR2=0.132 4.     

The catalytic incineration of (CH3)2S and its mixture with CH(3)SH over a Pt/Al(2)O(3) catalyst

Catalytic incineration is one of the cost-effective technologies to solve the troublesome volatile organic compounds (VOCs). However, some sulfur containing VOCs, such as dimethyl sulfide, may deactivate the Pt catalyst that is commonly used in the catalytic incineration process. This paper provides information on the poisoning effect of (CH3)2S. The catalytic incineration of (CH3)2S, typically emitted from the petrochemical industry, over a Pt/Al(2)O(3) fixed bed catalytic reactor was studied. The effects of operating parameters including inlet temperature, space velocity, (CH3)2S concentration, O2 concentration and catalyst size were characterized. Catalytic incineration on a mixture of (CH3)2S with CH(3)SH was also tested. The results show that the conversions of (CH3)2S increase as the inlet temperature increases and the space velocity decreases. The higher the (CH3)2S concentration is, the lower its conversion is. The O2 concentration has a positive effect on the conversion of (CH3)2S. (CH3)2S has a poisoning effect on the Pt/Al(2)O(3) catalyst, especially at lower temperatures. The conversion of (CH3)2S is significantly suppressed by the existence of CH(3)SH.     

Dry sol-gel condensation of p-X-C6H4SiH3 (X = H, CH3, CH3O, F, Cl) to organosilica p-X-C6H4SiO3 using nickelocene

The dry sol-gel reaction at toluene in ambient air atmosphere of p-X-C6H4SiH3 (X = H, CH3, CH3O, F, Cl) to p-C6H4SiO3 in high yield, catalyzed by nickelocene, is reported. The highest yield, molecular weight, polydispersity index, and TGA residue yield were obtained for p-Cl-C6H4SiH3. Some degree of unreacted Si-H bonds still remained in the gel because of steric reason. All the insoluble gels adopt an amorphous structure with a smooth surface. A plausible mechanism for the dry sol-gel reaction was suggested.     

Extended range near-infrared imaging of water and oil in facial skin

Recently, near-infrared (NIR) imaging has been applied to detecting changes in skin hydration using the water OH band centered near 1460 nm. However, assigning changes in the intensity of the OH band near 1460 nm to changes in the skin's water content is complicated. Consequently, detection of small changes in facial skin water content is difficult. For highly sensitive imaging of facial skin water and oil, a near-infrared unit with a large detection range that includes the CH(3) and CH(2) stretching vibration modes at 1700-1800 nm and the strongest water bands centered near 1920 nm is required. In this study, an extended range indium gallium arsenide near-infrared camera was combined with a diffuse-illumination unit specifically developed for facial skin analysis. Images of water and oil in facial skin were obtained in real time using a combination of interference filters, such as 1950 ± 56 nm for water OH, 1775 ± 50 nm for oil CH, and 1300 ± 40 nm for background reflections. Clear near-infrared images were obtained with little mirror reflection. The water and oil content of facial skin could be evaluated even around the eyes, nose, and sides of the cheeks, which are areas that are difficult to analyze using current commercial devices. Differences were detected in the time-dependent changes of water and oil content in facial skin images obtained after the application of different types of moisturizer. The distribution of both water and oil in the facial skin could be visualized at the same time, and the images could be used to evaluate skin type and skin conditions.     

Spectro-imaging observations of H3+ on Jupiter

Narrow-band filter, high-spectral-resolution (0.2 cm(-1)) spectro-imaging infrared observations of Jupiter's auroral zones, acquired in October 1999 and October 2000 with the FTS/BEAR instrument at the Canada-France-Hawaii Telescope, have provided maps of the emission from the H2 S1(1) quadrupole line and several H3+ lines. H2 and H3+ emissions appear to be morphologically different, especially in the north, where the latter notably exhibits a 'hot spot' near lambdaIII = 150-170 degrees System III longitude. The spectra include a total of 14 H3+ lines, including two hot lines from the 3v2-v2 band, detected on Jupiter for the first time. They can be used to determine H3+ column densities, rotational (Trot) and vibrational (Tvib) temperatures. We find the mean Tvib of the v2 = 3 state to be lower (960 +/- 50 K) than the mean Trot in v2 = 2 (1170 +/- 75 K), indicating an underpopulation of the v2 = 3 level with respect to local thermodynamical equilibrium. Rotational temperatures and associated column densities are generally higher and lower, respectively, than inferred previously from v2 observations. These features can be explained by the combination of both a large positive temperature gradient in the sub-microbar auroral atmosphere and non-local thermal equilibrium effects affecting preferentially hot and combination bands. Spatial variations in line intensities are mostly owing to correlated variations in the H3+ column densities. The thermostatic role played by H3+ at ionospheric levels may provide an explanation. The exception is the northern 'hot spot', which exhibits a Tvib about 250 K higher than other regions.     

Diode laser sensor for measurements of CO, CO(2), and CH(4) in combustion flows

A diode laser sensor has been applied to monitor CO, CO(2), and CH(4) in combustion gases with absorption spectroscopy and fast extraction-sampling techniques. Survey spectra of the CO 3nu band (R branch) and the 2nu(1) + 2nu(2)(0) + nu(3) CO(2) band (R branch) near 6350 cm(-1) and H(2)O lines from the nu(1) + 2nu(2) and 2nu(2) + nu(3) bands in the spectral region from 6345 to 6660 cm(-1) were recorded and compared with calculated spectra (from the HITRAN 96 database) to select optimum transitions for species detection. Species concentrations above a laminar, premixed, methane-air flame were determined from measured absorption in a fast-flow multipass absorption cell containing probe-sampled combustion gases; good agreement was found with calculated chemical equilibrium values.