OH Peak Research Articles

Effect of hydrogen addition on the OH* and CH* chemiluminescence emissions of premixed combustion of methane-air mixtures

Chemiluminescence emissions measurements of OH* and CH* are used to characterize the combustion of blends of methane and hydrogen in air in a constant volume combustion bomb, with two sets of initial conditions. The combined results of combustion development cover from 0.1 to 2.5 MPa. Burning velocity, heat release and unburned/burned gas temperatures are obtained from the pressure by using a two-zone thermodynamic combustion diagnostic model. Intensity of OH* and CH* increases with the initial temperature and the percentage of hydrogen, in parallel with the usual increase in burning velocity. The timings of the peaks of OH* and CH* chemiluminescence emissions are found to correlate respectively with the maximum rate of heat release and flame temperature. These results show that both chemiluminescence signals can be used to monitorize the burning process in combustion devices operating in the pressure range studied.

Electronic Effects of Ligand Substitution in a Family of CoII2 PARACEST pH Probes.

We report three new Co2-based paramagnetic chemical exchange saturation transfer (PARACEST) probes with the ability to ratiometrically quantitate pH. A CoII2 complex, [LCo2(etidronate)]-, featuring tetra(carboxamide) and OH-substituted etidronate ligands with opposing pH-dependent CEST peak intensities, was previously shown to exhibit a linear correlation between log(CESTOH/CESTNH) and pH in the pH range 6.5-7.6 that provided a sensitivity of 0.99(7) pH unit-1 at 37 °C. Here, we demonstrate through a series of CF3-functionalized CoII2 complexes [(XL')Co2(etidronate)]- (X = NO2, F, Me), that modest changes in the electronic structure of CoII centers through remote ligand substitution can significantly affect the NMR and CEST properties of Co2-based PARACEST probes. Variable-pH NMR and CEST analyses reveal that the chemical shifts of the ligand protons are highly affected by the nature of the X substituent. The ratios of OH and NH CEST peak intensities at 115 and 88, 93 and 79, and 88 and 76 ppm for X = NO2, F, and Me, respectively, afford pH calibration curves with remarkably high sensitivities of 1.49(9), 1.48(7), and 2.04(5) pH unit-1 across the series. The 1.5-2-fold enhancement in pH sensitivity for the CF3-functionalized Co2 probes stems from the complete separation of the OH and NH CEST peaks. Furthermore, incorporation of electron-withdrawing CF3 groups shifts the detection window to a more acidic range of pH 6.2-7.4. Finally, the CoII2 complexes are found to be extremely robust toward substitution and oxidation in aqueous solutions. Taken together, these results highlight the unique ability of transition metal-based PARACEST probes to provide a highly sensitive concentration-independent measure of pH and demonstrate that modest ligand modifications can be a powerful tool for optimizing the pH sensing performance of these probes.

Synthesis, physicochemical characterizations and in vitro biological evaluations of amide based Zn(II) carboxylates

Carboxylate ligands are widely used in chemistry and pharmacy owing to their ability to form stable complexes with a large variety of metal ions. In that context, carboxylate complexes allow modulation of the pharmaceutical products. Herein, a series of six novel Zn(II) carboxylates: [Zn(L1)2] (1), [Zn(L1)2 (bipy)] (2), [Zn(L1)2 (phen)] (3), [Zn(L2)2] (4), [Zn(L2)2 (bipy)] (5) and [Zn(L2)2 (phen)] (6) (where L1 = 4-(2-methoxy-5-nitrophenylamino)-4-oxobutanoic acid), L2 = 4-(2-nitro-4-methoxyphenylamino)-4-oxobutanoic acid), phen = 1,10-phenanthroline and bipy = 2,2′-bipyridine) were synthesized in good yield and successfully characterized by 1H, 13C NMR, FT-IR and single-crystal X-ray crystallography. The spectroscopic data reveal that the absence of OH peak in the spectra of complexes confirm their formation. Single-crystal X-ray crystallographic data for complexes 1 and 5 show a distorted octahedral environment around the Zn atom. The results of both FT-IR and single-crystal X-ray crystallography confirm the bidentate nature of the carboxylate ligands. The DNA interaction study of the synthesized complexes was investigated using UV–visible spectroscopy and viscosity measurements suggesting an intercalative binding mode of interaction of the complexes with SS-DNA. The interaction between the synthesized complexes and CTAB was elaborately studied with a conductometric method. The conductivity method was used to find CMC, higher CMC values suggesting a stable complex-CTAB system. Results of in vitro antibacterial and antifungal activities indicate the biological potency of the synthesized compounds.

Application of SWIR spectrometry to the determination of biotite compositions in hydrothermally altered units of the Yangyang iron-oxide-apatite (IOA) deposit, South Korea

The Yangyang iron oxide-apatite deposit in South Korea has gone through multiple events for igneous activity, structural evolution, hydrothermal alteration, and mineralization. Trioctahedral mica is indicative of potassic alteration in the Yangyang IOA deposit and its mineral chemistry is quite variable. The variability can be described in terms of biotite colors and short wavelength infrared (SWIR) reflectance spectra. Brown to greenish brown biotite displays lower values of Mg# (0.48–0.58) than green biotite (0.62–0.78), whereas colorless phlogopite related to Fe–P mineralization has the highest values of Mg# (0.85–0.95). To compare Mg# values with the positions and intensities of absorption in the trioctahedral micas, we used three types of spectrum: reflectance, hull quotient, and Gaussian. Brown biotite produces a short Mg–OH peak near 2340 nm, green biotite has a peak near 2330 nm, and colorless phlogopite displays an absorption peak near 2310 nm. These positional variations are consistent with compositional changes. A mica alteration index (MAI) represents the ratio of Fe–OH and Mg–OH peak absorption intensities for trioctahedral micas. From brown to green biotite and colorless phlogopite, the MAI values gradually increase with decreasing Fe–OH intensity. Correlation coefficients for plots of Mg–OH absorption values vs. Mg# vary from 0.89 for the reflectance method, to 0.93 for the hull quotient method, and 0.93 for the Gaussian method, and for plots of MAI vs. Mg# they vary from 0.91 for the reflectance method, to 0.92 for the hull quotient method, and 0.92 for the Gaussian method. Analyses using our new SWIR spectroscopic methods confirm that the abundance of indicator minerals and the Fe:Mg ratios in trioctahedral micas vary systematically as a function of hydrothermal fluid chemistry and mineral composition within the altered lithologies. SWIR spectroscopy of trioctahedral micas could provide a useful tool for mapping vectors of alteration in the Yangyang IOA system.

Wall chemical effect of metal surfaces on DME/air cool flame in a micro flow reactor

Wall chemical effect on DME/air weak flames (Uin = 1.5 cm/s, ϕ = 0.85) was investigated using a micro flow reactor with a streamwise temperature gradient experimentally. The quartz channel used in this study has a rectangular cross-section of 1.5 × 5 mm, which offers a good optical access for the planar laser-induced fluorescence (PLIF) measurement. The walls can be replaced for examining wall chemical effects of different wall materials. Wall surface materials, quartz, SiC, type 321 stainless steel (SUS321), iron, nickel and chromium, were employed. For SiC, SUS321 and metals, a 150-nm-thick film is deposited on the inner surface of the quartz channel to achieve different wall chemical boundary with identical thermal boundary condition. Streamwise distributions of DME, CO and CO2 in the weak flame were measured with the gas chromatography (GC), and HCHO and OH distributions were measured through PLIF. It is found that species distributions in both the low- and high-temperature oxidation zones of the weak flame are significantly altered for different wall surface materials. Comparing with that in the quartz and SiC-coated channel, DME in the SUS321-coated channel has a much higher concentration in the negative temperature coefficient (NTC) region, while CO and HCHO have lower concentrations. The peak of OH is shifted downstream, and so as the rising of CO2. According to the results of the pure metal-coated channels, iron and nickel in the SUS321 should be responsible for the changes. These results suggest that the wall chemical effect of metal may exert strong influence on the low-temperature oxidation, which changes the species pool in the cool flame and leads to a modification of the hot flame region downstream.

Temperature Dependence of the Air/Water Interface Revealed by Polarization Sensitive Sum-Frequency Generation Spectroscopy.

The temperature dependence of the vibrational sum-frequency generation (vSFG) spectra of the air/water interface is investigated using many-body molecular dynamics (MB-MD) simulations performed with the MB-pol potential energy function. The vSFG spectra calculated for different polarization combinations are then analyzed in terms of molecular autocorrelation and cross-correlation contributions. To provide molecular-level insights into interfacial hydrogen-bonding topologies, which give rise to specific spectroscopic features, the vSFG spectra are further investigated by separating contributions associated with water molecules donating zero, one, or two hydrogen bonds to neighboring water molecules. This analysis suggests that the low frequency shoulder of the free OH peak which appears at ∼3600 cm-1 is primarily due to intermolecular couplings between both singly and doubly hydrogen-bonded molecules.

Mesospheric front observations by the OH airglow imager carried out at Ferraz Station on King George Island, Antarctic Peninsula, in 2011

Abstract. The main goals of this work are to characterize and investigate the potential wave sources of four mesospheric fronts identified in the hydroxyl near-infrared (OH-NIR) airglow images, obtained with an all-sky airglow imager installed at Comandante Ferraz Antarctic Station (EACF, as per its Portuguese acronym) located on King George Island in the Antarctic Peninsula. We identified and analyzed four mesospheric fronts in 2011 over King George Island. In addition, we investigate the atmospheric background environment between 80 and 100 km altitude and discuss the ducts and propagation conditions for these waves. For that, we used wind data obtained from a meteor radar operated at EACF and temperature data obtained from the TIMED/SABER satellite. The vertical wavenumber squared, m2, was calculated for each of the four waves. Even though no clearly defined duct (indicated by positive values of m2 sandwiched between layers above and below with m2 < 0) was found in any of the events, favorable propagation conditions for horizontal propagation of the fronts were found in three cases. In the fourth case, the wave front did not find any duct support and it appeared to dissipate near the zenith, transferring energy and momentum to the medium and, consequently, accelerating the wind in the wave propagation direction (near to south) above the OH peak (88–92 km). The likely wave sources for these four cases were investigated by using meteorological satellite images and in two cases we could find that strong instabilities were potential sources, i.e., a cyclonic activity and a large convective cloud cell. In the other two cases it was not possible to associate troposphere sources as potential candidates for the generation of such wave fronts observed in the mesosphere and secondary wave sources were attributed to these cases. Keywords. Atmospheric composition and structure (airglow and aurora) – meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)

Distinguishing Surface versus Bulk Hydroxyl Groups of Cellulose Nanocrystals Using Vibrational Sum Frequency Generation Spectroscopy.

In plant cell walls and cellulose-containing composites, nanocrystalline cellulose interacts with water molecules or matrix polymers through hydrogen bonding of the hydroxyl groups at the cellulose surface. These interactions play key roles in cellulose assembly in plant cell walls and mechanical properties of cellulose composites; however, they could not be studied properly due to the spectroscopic difficulty of selectively detecting the surface hydroxyl groups of nanocrystalline domains. This study employed the sum frequency scattering principle to distinguish the hydroxyl groups inside of the crystalline nanodomain of cellulose and those exposed at the surface of crystalline domains. The comparison of the spectra at various scattering angles revealed that the OH peak near ∼3450 cm-1 comes from the weakly hydrogen-bonded OH groups at the surface of crystalline cellulose. Also, a time delay measurement found that the sharp vibrational features observed near 3700 cm-1 can be attributed to isolated OH groups not accessible by ambient water molecules. These findings allow the distinction of surface versus bulk OH groups in sum frequency generation vibrational spectroscopy.

1,8-bis(2-hydroxy-3,5-di-tert-butylbenzyl)-4,11-dibenzyl-1,4,8,11-tetraazacyclotetradecane

A cyclam (1,4,8,11-tetraazacyclotetradecane)-based macrocycle bearing two benzyl and two 2-hydroxy-3,5-di-tert-butylbenzyl pendent arms was synthesized and characterized using spectroscopic techniques and single crystal X-ray diffraction. The macrocycle crystallizes in the triclinic space group P-1, with the asymmetric unit containing one-half of the molecule. The structure is stabilized by hydrogen-bonding which exists between the phenolic protons and the nitrogen atoms of the macrocyclic ring. The presence of this hydrogen bonding is observed in the 1H-NMR due to the deshielded nature of the phenolic OH peak (δ 9.99). Cyclic voltammetry of the ligand revealed a single quasi-reversible peak at −0.58 V (Epc = −0.48 V and Epa = −0.68 V), which is due to the electrochemical oxidation of the phenol to the phenoxyl radical.

Effects of mechanical activation on the co-liquefaction of Xigou sub-bituminous coal from Xinjiang and Karamay petroleum vacuum residues

The effects of mechanical activation on the co-liquefaction of Xigou sub-bituminous coal (XSBC) and a mixture solvent of creosote oil and Karamay petroleum vacuum residues were investigated. The structure of the mechanically activated coal was more porous than the structure of XSBC according to the characterization results. Compared to XSBC, the average pore size of the activated coal increased by 106.7%, whereas the specific surface area decreased by 74.7%. The absorption peaks of OH at 3300cm−1 and CO at 1720–1650cm−1 decreased. The ratio of the fractions of aromatic carbon and sp2-hybridized carbon decreased by 13%. The mass loss from 100°C to 300°C increased by 237% and the apparent activation energy in the liquefaction temperature range of 300–400°C decreased by 21.6%. The yields of total oil, asphaltene and preasphaltene (A+PA), gas and residue of mechanical activated coal slurry were 82.67, 10.80, 4.12 and 2.40%, respectively. Compared to raw coal slurry, the total oil yield and the gas yield of activated coal slurry increased by 8.2 and 63.5%, respectively, whereas the A+PA yield and the residue yield decreased by 29.9 and 57.5%, respectively. The H2 consumption decreased by 19.9%. Moreover, the yield of heavy oil and distillate in the liquefied product decreased by 51.1 and 31.3%, respectively, whereas the yields of gasoline and diesel increased by 65.5 and 10.7%, respectively.

Some IR features of SiO4 and OH in coesite, and its amorphization and dehydration at ambient pressure

Coesite (Coe) with grain size in the range of 30–80μm has been synthesized at 5GPa and 1600°C for 12h by using a cubic press. Its unpolarized single-crystal absorption infrared (IR) spectra show 14 IR bands in the range of ∼1200–650cm−1, five of which have high intensity (at ∼1161, 1109, 1063, 1028 and 994cm−1) and are preliminarily assigned to the SiO4 asymmetric stretching (ν3). In addition, three sharp but relatively weak bands at ∼838, 814 and 796cm−1 are tentatively attributed to the SiO4 asymmetric bending (ν4). The IR data also show six OH peaks in the range of 3700–3300cm−1, with an estimated H2O content of ∼30(4)wt ppm. Following previous studies, we have assigned the peaks at ∼3464 (#7), 3421 (#8), 3406 (#9) and 3377cm−1 (#10) to the Type-II hydrogarnet substitution, and the peaks at ∼3500 (#6a) and 3534cm−1 (#6b) to the B-based defects, with the latter aroused by possible B contamination in the synthesizing experiments. Annealing experiments conducted consecutively at ∼200, 400, 600, 800, 1000 and 1200°C, with every heating step lasting for 24h, demonstrate that water diffuses quickly out of Coe at T as low as ∼600°C. The material annealed at 1200°C is completely dehydrated and amorphous. A quick response of the water content in Coe to the changes of P, T and composition is thus possible, which may be critical to the preservation of natural Coe in relevant geological processes. It further implies that water in Coe, and possibly in other nominally anhydrous minerals (NAMs), may behave distinctively different from the water located in the hydrous phases such as amphibole and mica, and potentially makes significant contribution to the subduction zone-related fluids.

Quantum Mechanical Calculations of Vibrational Sum-Frequency-Generation (SFG) Spectra of Cellulose: Dependence of the CH and OH Peak Intensity on the Polarity of Cellulose Chains within the SFG Coherence Domain.

Vibrational sum-frequency-generation (SFG) spectroscopy is capable of selectively detecting crystalline biopolymers interspersed in amorphous polymer matrices. However, the spectral interpretation is difficult due to the lack of knowledge on how spatial arrangements of crystalline segments influence SFG spectra features. Here we report time-dependent density functional theory (TD-DFT) calculations of cellulose crystallites in intimate contact with two different polarities: parallel versus antiparallel. TD-DFT calculations reveal that the CH/OH intensity ratio is very sensitive to the polarity of the crystallite packing. Theoretical calculations of hyperpolarizability tensors (βabc) clearly show the dependence of SFG intensities on the polarity of crystallite packing within the SFG coherence length, which provides the basis for interpretation of the empirically observed SFG features of native cellulose in biological systems.

Testing Atmospheric Oxidation in an Alabama Forest

Abstract The chemical species emitted by forests create complex atmospheric oxidation chemistry and influence global atmospheric oxidation capacity and climate. The Southern Oxidant and Aerosol Study (SOAS) provided an opportunity to test the oxidation chemistry in a forest where isoprene is the dominant biogenic volatile organic compound. Hydroxyl (OH) and hydroperoxyl (HO2) radicals were two of the hundreds of atmospheric chemical species measured, as was OH reactivity (the inverse of the OH lifetime). OH was measured by laser-induced fluorescence (LIF) and by taking the difference in signals without and with an OH scavenger that was added just outside the instrument’s pinhole inlet. To test whether the chemistry at SOAS can be simulated by current model mechanisms, OH and HO2 were evaluated with a box model using two chemical mechanisms: Master Chemical Mechanism, version 3.2 (MCMv3.2), augmented with explicit isoprene chemistry and MCMv3.3.1. Measured and modeled OH peak at about 106 cm−3 and agree well within combined uncertainties. Measured and modeled HO2 peak at about 27 pptv and also agree well within combined uncertainties. Median OH reactivity cycled between about 11 s−1 at dawn and about 26 s−1 during midafternoon. A good test of the oxidation chemistry is the balance between OH production and loss rates using measurements; this balance was observed to within uncertainties. These SOAS results provide strong evidence that the current isoprene mechanisms are consistent with measured OH and HO2 and, thus, capture significant aspects of the atmospheric oxidation chemistry in this isoprene-rich forest.

Effects of N2, CO2 and H2O dilutions on temperature and concentration fields of OH in methane Bunsen flames by using PLIF thermometry and bi-directional PLIF

The effects of N2, CO2 and H2O dilutions on the two-dimensional (2D) temperature and concentration fields of OH in methane Bunsen flames were investigated by employing two-line planar laser-induced fluorescence (PLIF) thermometry and bi-directional PLIF technique, respectively. The spatial resolution of the measured temperature and concentration fields of OH radical was 41.7μm. It was found that the measured temperature fields in methane Bunsen flames with different diluents exhibited a non-uniform and a symmetrical structure. In terms of decreasing the flame temperature, the CO2 diluent achieved a good result compared with N2 and H2O diluents. The total uncertainties in PLIF thermometry measurements were estimated to be ±8.44%, ±8.17% and ±8.27% for each diluent, respectively. The OH peak absorption cross sections at different heights were obtained in methane Bunsen flames with different diluents. Finally, the 2D absolute OH concentration filed in methane Bunsen flames diluted with three different diluents were obtained by using bi-directional PLIF technique. The peak absolute OH number densities in the flames with H2O, N2 and CO2 diluents were 9.84×1017cm−3, 8.57×1017cm−3 and 7.84×1017cm−3, with the overall uncertainties of ±20.56%, ±19.04% and ±23.43%, respectively. The numerical simulations of chemical kinetics were performed by using a physical model of one-dimensional laminar premixed flame and a detail methane reaction mechanism of GRI-Mech 3.0 so as to investigate the difference between the simulation results and experimental values. The comparison results for the temperature and OH concentration indicated that the reaction mechanism of GRI-Mech 3.0 might underestimate the chemical effects of CO2 and H2O diluents on the production of OH radical in premixed methane flames.

Effect of different pretreatments on the thermal degradation of seaweed biomass

This study aims to investigate the pyrolysis characteristics of seaweed biomass (Enteromorpha) after water-washed and acid-washed (7%, 10% of hydrochloric acid, 7% of sulfuric acid, 7% of phosphoric acid) pretreatments. These pretreatments of seaweed were signifi after water-washed and acid-washed (7%, 10, Ca, Na and Mg metals. Among these pretreatments the removal capacity of H2SO4 was the most obvious. The pyrolysis behaviors of materials after pretreatments have been studied using thermogravimetry-mass spectroscopy. During the pretreatments, OH, CO/CH, SO and CO functional groups in Enteromorpha were cleaved. Phosphoric acid and hydrochloric acid made the intensities of the absorption peaks of OH and SO decrease the most obvious, respectively. Therefore, there was almost no NO2 and SO2 emission in the process of pyrolysis of Enteromorpha washed by hydrochloric acid and phosphoric acid. The volatile components of Enteromorpha were easy to evolve after the pretreatment. Sulfuric acid exhibited the best efficiency in the process of pyrolysis, and it manifested smaller influence on other volatile organics simultaneously. However, the maximum weight loss rate and the corresponding temperature reduced after pretreatments, and the maximum weight loss rate reduced more distinctly after 7% hydrochloric acid treatment. These results suggest that selective acid pretreatment would facilitate the thermal conversion of seaweed biomass.

Biobased blends of poly(propylene carbonate) and poly(hydroxybutyrate‐co‐hydroxyvalerate): Fabrication and characterization

ABSTRACTPoly(propylene carbonate) (PPC), a CO2‐based bioplastic and poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) were melt blended followed by injection molding. Fourier transform infrared spectroscopy detected an interaction between the macromolecules from the reduction in the OH peak and a shift in the CO peak. The onset degradation temperature of the polymer blends was improved by 5% and 19% in comparison to PHBV and PPC, respectively. Blending PPC with PHBV reduced the melting and crystallization temperatures and crystallinity of the latter as observed through differential scanning calorimetry. The amorphous nature of PPC affected the thermal properties of PHBV by hindering the spherulitic growth and diluting the crystalline region. Scanning electron micrographs presented a uniform dispersion and morphology of the blends, which lead to balanced mechanical properties. Incorporating PHBV, a stiff semi‐crystalline polymer improved the dimensional stability of PPC by restricting the motion of its polymer chains. © 2016 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44420.

Rapid prediction of moisture content of quinoa (Chenopodium quinoa Willd.) flour by Fourier transform infrared (FTIR) spectroscopy

Moisture content determination on quinoa flour is actually performed by gravimetric analysis, which is time, energy consuming and sample destructive. An emerging technique to measure moisture in an innovative way avoiding those problems is the Fourier transform infrared (FTIR) spectroscopy. The aim of this study is to obtain a trustable and validated model to predict moisture content of quinoa flour using FTIR. To perform the moisture measurements in five quinoa ecotypes, a gravimetric data and area under the curve obtained by FTIR, considering the OH peak associated to water (3200 cm−1), were compared at five different relative humidities (0, 33, 58, 75 and 100%). A good correlation between gravimetric measurements and FTIR area were observed (R2 = 0.8729) and no differences were observed between quinoa ecotypes. A cross validation technique to predict moisture considering experimental and predicted data by area under de curve by FTIR was performed obtaining a general equation (y = 35.73x + 46.04) with a high repetitively and good prediction (100%) of the tested models.

Characterization of process-induced damage in Cu/low-k interconnect structure by microscopic infrared spectroscopy with polarized infrared light

Microscopic Fourier-transform infrared (FT-IR) spectra are measured for a Cu/low-k interconnect structure using polarized IR light for different widths of low-k spaces and Cu lines, and for different heights of Cu lines, on Si substrates. Although the widths of the Cu line and the low-k space are 70 nm each, considerably smaller than the wavelength of the IR light, the FT-IR spectra of the low-k film were obtained for the Cu/low-k interconnect structure. A suitable method was established for measuring the process-induced damage in a low-k film that was not detected by the TEM-EELS (Transmission Electron Microscope-Electron Energy-Loss Spectroscopy) using microscopic IR polarized light. Based on the IR results, it was presumed that the FT-IR spectra mainly reflect the structural changes in the sidewalls of the low-k films for Cu/low-k interconnect structures, and the mechanism of generating process-induced damage involves the generation of Si-OH groups in the low-k film when the Si-CH3 bonds break during the fabrication processes. The Si-OH groups attract moisture and the OH peak intensity increases. It was concluded that the increase in the OH groups in the low-k film is a sensitive indicator of low-k damage. We achieved the characterization of the process-induced damage that was not detected by the TEM-EELS and speculated that the proposed method is applicable to interconnects with line and space widths of 70 nm/70 nm and on shorter scales of leading edge devices. The location of process-induced damage and its mechanism for the Cu/low-k interconnect structure were revealed via the measurement method.

Study of the auto-ignition phenomenon of PRFs under HCCI conditions in a RCEM by means of spectroscopy

An investigation of the effects of contour conditions and fuel properties on the auto-ignition and combustion process under HCCI conditions is presented in this study. A parametric variation of initial temperature, intake pressure, compression ratio, oxygen concentration and equivalence ratio has been carried out for Primary Reference Fuels in a Rapid Compression Expansion Machine while applying spectroscopy. The results have also been contrasted with natural chemiluminescence measurements. Additionally, the experiments have been simulated in CHEMKIN and the results derived from the optical techniques have been compared with the results from the chemical kinetics of the process, validating the chemical kinetic mechanism and an additional sub-model of excited OH∗. Two different scenarios can be seen according to the results from the spectrograph. For very lean or very low-temperature combustions no peak of OH∗ is seen at 310nm of wavelength, proving that the luminosity came from the CO continuum rather than from the OH∗. However, for more intense combustions (richer equivalence ratios, higher temperatures or lower EGR rates) spectrography shows a clear peak of OH∗ that has much longer time of life than the corresponding to the CO continuum. The main chemical reaction that causes this two scenarios has been identified as H+HO2⇒2OH. The increase of relevance of this reaction at high combustion temperatures causes a higher OH∗ accumulation, which leads to a brighter OH∗ emission. Finally, for low temperature combustions the CO continuum out-shines the OH∗ radiation so the light emitted by this radical cannot be detected by means of natural chemiluminescence.

Vibrational Sum Frequency Generation Spectroscopy Study of Hydrous Species in Soda Lime Silica Float Glass.

It is generally accepted that the mechanical properties of soda lime silica (SLS) glass can be affected by the interaction between sodium ions and hydrous species (silanol groups and water molecules) in its surface region. While the amount of these hydrous species can be estimated from hydrogen profiles and infrared spectroscopy, their chemical environment in the glass network is still not well understood. This work employed vibrational sum frequency generation (SFG) spectroscopy to investigate the chemical environment of hydrous species in the surface region of SLS float glass. SLS float glass shows sharp peaks in the OH stretching vibration region in SFG spectra, while the OH stretch peaks of glasses that do not have leachable sodium ions and the OH peaks of water molecules in condensed phases are normally broad due to fast hydrogen bonding dynamics. The hydrous species responsible for the sharp SFG peaks for the SLS float glass were found to be thermodynamically more stable than physisorbed water molecules, did not exchange with D2O, and were associated with the sodium concentration gradient in the dealkalized subsurface region. These results suggested that the hydrous species reside in static solvation shells defined by the silicate network with relatively slow hydrogen bonding dynamics, compared to physisorbed water layers on top of the glass surface. A putative radial distribution of the hydrous species within the SLS glass network was estimated based on the OH SFG spectral features, which could be compared with theoretical distributions calculated from computational simulations.