The Raman spectra and cross-sections of H2O, D2O, and HDO in the OH/OD stretching regions

We report the OH and OD stretching regions of the vapor phase Raman spectra of H₂O, and of a D₂O/HDO mixture, at room temperature. Also, the corresponding spectrum of H₂O at ∼2000 K in a methane/air flame is reported. These spectra are interpreted in terms of transition moments of the molecular polarizability, based on high-level ab initio calculations of the polarizability surface, and on variational wavefunctions considering the rotational-vibrational coupling in full. As a byproduct of this analysis several tables have been compiled including scattering strengths and assignments for individual rotational transitions of the three species. From these tables the Raman spectra in the OH/OD stretching regions can be simulated over the range of temperatures up to 2000 K for H₂O, and up to 300 K for D₂O and HDO.     

The Raman spectra and cross-sections of the ν2 band of H2O, D2O, and HDO

We report the experimental Raman spectra of the ν₂ band of H₂O, D₂O, and HDO in the vapor phase at room temperature. A complete interpretation of the Raman intensities is carried out employing the variational rovibrational wavefunctions obtained from a Hamiltonian in Radau coordinates and an ab initio polarizability surface at 514.5 nm. We show the importance of the rotation-vibration coupling to obtain the correct line intensities. Several tables with the assignments of the individual rotational-vibrational transitions and their Raman scattering strengths are reported. From these tables, the ν₂ Raman spectra can be simulated up to 2000 K for H₂O, and up to 300 K for D₂O and HDO.     

The rotational Raman spectra and cross sections of H2O, D2O, and HDO

We report the experimental rotational Raman spectra of H₂O, and of a mixture of D₂O and HDO in the vapor phase at room temperature, and their interpretation in terms of rotational–vibrational energies, wavefunctions, and transition moments of the molecular polarizability. These transition moments are based on high-level ab initio calculations of the wavelength dependent polarizability surface, and on wavefunctions where the rotational–vibrational coupling is considered in detail. As a byproduct of this analysis several tables have been compiled including scattering strengths and assignments for individual rotational transitions of the three species. From these tables the rotational Raman spectra can be simulated over the range of temperatures up to 2000 K for H₂O, and up to 300 K for D₂O and HDO.     

The location of excess electrons on H2O/TiO2(110) surface and its role in the surface reactions

Excess electrons play a key role in many of the properties of Titanium dioxide (TiO₂). Understanding their behaviour is important for improving the performance of TiO₂ in energy-related applications. Here, we describe a DFT + U study of the locations of the unpaired electron (UPE) on rutile TiO₂(110) (R-TiO₂(110)) surface and H₂O/R-TiO₂(110) surface. Our results show that the subsurface are preferred with R-TiO₂(110) surface. In contrast to previous studies, we find that the UPE tends to migrate to the surface H₂O-Ti_5c (the five-coordinated titanium (Ti_5c) at surface with H₂O adsorption) with the increasing of H₂O coverage and UPE concentration. In addition, we have shown that the UPE plays an important role in the O-H bond dissociation and other important elementary reactions in photo-catalytic H₂O dissociation on R-TiO₂(110) such as H, OH and H₂ desorption. Specifically, it enhances the O-H bond dissociation, as well as H and H₂ desorption from bridging hydroxyl and Ti_5c-OH (the Ti_5c with OH adsorption), but hinders the OH and H desorption from Ti_5c. We believe our results afford a further understanding of the adsorbent dependent UPE migration, and the role of UPE in the surface reactions.     

Flame structure studies of rich ethylene-oxygen-argon mixtures doped with CO2, or with NH3, or with H2O

Structures of several premixed ethylene-oxygen-argon rich flat flames burning at 50 mbar have been established by using molecular beam mass spectrometry in order to investigate the effect of CO₂, or NH₃, or H₂O addition on species concentration profiles. The aim of this study is to examine the eventual changes of profiles of detected hydrocarbon intermediates which could be considered as soot precursors (C₂H₂, C₄H₂, C₅H₄, C₅H₆, C₆H₂, C₆H₄, C₆H₆, C₇H₈, C₆H₆O, C₈H₆, C₈H₈, C₉H₈ and C₁₀H₈). The comparative study has been achieved on four flames with an equivalence ratio (f) of 2.50: one without any additive (F2.50), one with 15% of CO₂ replacing the same quantity of argon (F2.50C), one with 3.3% of NH₃ in partial replacement of argon (F2.50N) and one with 13% of H₂O in replacement of the same quantity of argon (F2.50H). The four flat flames have similar final flame temperatures (1800 K).CO₂, or NH₃, or H₂O addition to the fresh gas inlet causes a shift downstream of the flame front and thus flame inhibition. Endothermic processes CO₂ + H = CO + OH and H₂O + H = H₂ + OH are responsible of the reduction of the hydrocarbon intermediates in the CO₂ and H₂O added flames through the supplementary formation of hydroxyl radicals. It has been demonstrated that such processes begin to play at the end of the flame front and becomes more efficient in the burnt gases region.The replacement of some Ar by NH₃ is responsible only for a slight decrease of the maximum mole fraction of C₂H₂, but NH₃ becomes much more efficient for C₄H₂ and C₅ to C₁₀ species. Moreover, the efficiency of NH₃ as a reducing agent of C₅ to C₁₀ intermediates is larger than that of CO₂ and H₂O for equal quantities added.     

High sensitivity ICLAS of H2O in the 12,580-13,550 cm transparency window

High-sensitivity Intracavity Laser Absorption Spectroscopy (ICLAS) is used to measure the high resolution absorption spectrum of H₂¹⁸O between 12,580 and 13,550 cm⁻¹. This spectral region covers the 3v+δ polyad of very weak absorption. Four isotopologues of water (H₂¹⁸O, H₂¹⁶O, H₂¹⁷O, HD¹⁸O) are found to contribute to the observed spectrum. Spectrum analysis is performed with the aid of variational calculations and allowed for assigning 1126 lines belonging to H₂¹⁸O, while only 160 H₂¹⁸O lines are included in the HITRAN-2008 database. Altogether, 823 accurate energy levels of H₂¹⁸O are determined from transitions attributed to 26 upper vibrational states, 438 of them being reported for the first time. New information includes energy levels of four newly observed vibrational states of H₂¹⁸O: (2 4 0), (1 4 1), (0 4 2) and (2 3 1) at 13,167.718, 13,212.678, 13,403.71 and 15,073.975 cm⁻¹, respectively. H₂¹⁸O transitions involving highly excited bending states like (1 6 0), (0 6 1), (0 7 1), (1 7 0), (0 9 0) and even (0 10 0) have been identified as a result of an intensity borrowing from stronger bands via high-order resonance interactions. Thirty-six new energy levels of H₂¹⁷O, present with a 2% relative concentration in our sample, could be determined. The rotational structure of the (0 2 3) state of HD¹⁸O at 13,245.497 cm⁻¹ is also reported for the first time.     

Si在水汽中氧化传质机制的H218O/H216O同位素示踪研究

采用同位素H₂¹⁶O/H₂¹⁸O接续氧化同位素示踪方法,研究了单晶硅在1100 ℃水汽中氧化的微观传质机制.在H₂¹⁶O,H₂¹⁸O分别氧化和H₂¹⁶O/H₂¹⁸O接续氧化处理后,研究氧化产物形态和结构.并用二次离子质谱仪(SIMS)研究了同位素 关键词： 同位素示踪 2¹⁸O')" href="#">H₂¹⁸O 替位扩散 硅     

Controlled synthesis of BaWO4 hierarchical nanostructures by exploiting oriented attachment in the solution of H2O and C2H5OH

Shape-controlled synthesis of BaWO₄ hierarchical nanostructures has been successfully achieved by exploiting oriented attachment in a mixture of water and ethanol. A controlled change in the volume ratio of C₂H₅OH and H₂O or the concentration of initial reagents has resulted in the synthesis of products of various morphologies, such as shuttle-like, ellipsoid-like, and flower-like ones. The obtained products are characterized by field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. The altered nucleation and growth rates of primary particles that assembled to the final hierarchical nanostructures through oriented attachment are the main cause of the evolution of their morphologies. The room-temperature photoluminescent intensities of the products strongly depend on their morphology.     

Solvent effects for CO and H2 adsorption on Cu2O (1 1 1) surface: A density functional theory study

To investigate solvent effects, CO and H₂ adsorption on Cu₂O (1 1 1) surface in vacuum, liquid paraffin, methanol and water are studied by using density functional theory (DFT) combined with the conductor-like solvent model (COSMO). When H₂ and CO adsorb on Cu_cus of Cu₂O (1 1 1) surface, solvent effects can improve CO and H₂ activation. The H-H bond increases with dielectric constant increasing as H₂ adsorption on O_suf of Cu₂O (1 1 1) surface, and the H-H bond breaks in methanol and water. It is also found that both the structural parameters and Mulliken charges are very sensitive to the COSMO solvent model. In summary, the solvent effects have obvious influence on the clean surface of Cu₂O (1 1 1) and the adsorptive behavior.     

The influence of temperature (20-1000 °C) on binary mixtures of solid solutions of CH3COOLi·2H2O-MgHPO4·3H2O

Thermally induced phase transitions (20-1000 °C) in the substrates and binary mixtures of CH₃COOLi·2H₂O(1)-MgHPO₄·3H₂O(11) have been analysed. Changes taking place on dehydration and thermal dissociation of binary mixtures prepared with percent molar ratios of 90-10% were studied by differential thermal analysis (TG, DTG, DTA), IR-spectroscopy and WAXS.The above-mentioned substrates changed their structure when heated for 1 h at 500 or 1000 °C. CH₃COOLi·2H₂O(1) (ID: 23-1171) changed the structure at 500 °C to that of Li₂CO₃ (ID: 22-1141), while at 1000 °C the structure was impossible to analyse as the compound reacted both with porcelain and with platinum (crucible materials). MgHPO₄·3H₂O(11) (Newberyite, ID: 35-780, 19-762) changed its structure at 500 °C to amorphous phase and at 1000 °C to Mg₂P₂O₇ (ID: 32-626).The following compounds were assayed in the respective binary mixtures heated at 500 °C for 1 h: 70% (1)-30%(11): LiMgPO₄ (ID: 18-735), MgO (ID: 4-829); 50%(1)-50%(11): LiMgPO₄ (ID: 18-735), Li₃PO₄ (ID: 25-1030); 30%(1)-70%(11): LiMgPO₄ (ID: 32-574); binary mixtures heated at 1000 °C contained the following compounds: 70%(1)-30%(11): LiMgPO₄ (ID: 32-574,18-735), Li₃PO₄ (ID: 15-760,25-1030), MgO (ID: 4-829); 50%(1)-50%(11): LiMgPO₄ (ID: 32-574, 18-735), MgO (ID: 4-829); 30%(1)-70%(11): LiMgPO₄ (ID: 18-735, 32-574), Mg₂P₂O₇ (ID: 22-1152, 8-38), Li₄SiO₄ (37-1472).     

Adsorption and dissociation of H2 on the Cu2O(1 1 1) surface: A density functional theory study

Interactions of atomic and molecular hydrogen with perfect and deficient Cu₂O(1 1 1) surfaces have been investigated by density functional theory. Different kinds of possible modes of H and H₂ adsorbed on the Cu₂O(1 1 1) surface and possible dissociation pathways were examined. The calculated results indicate that O_SUF, Cu_CUS and O_vacancy sites are the adsorption active centers for H adsorbed on the Cu₂O(1 1 1) surface, and for H₂ adsorption over perfect surface, Cu_CUS site is the most advantageous position with the side-on type of H₂. For H₂ adsorption over deficient surface, two adsorption models of H₂, H₂ adsorbing perpendicularly over O_vacancy site and H₂ lying flatly over singly-coordinate Cu-Cu short bridge, are typical of non-energy-barrier dissociative adsorption leading to one atomic H completely inserted into the crystal lattice and the other bounded to Cu_CUS atom, suggesting that the dissociative adsorption of H₂ is the main dissociation pathway of H₂ on the Cu₂O(1 1 1) surface. Our calculation result is consistent with that of the experimental observation. Therefore, Cu₂O(1 1 1) surface with oxygen vacancy exhibits a strong chemical reactivity towards the dissociation of H₂.     

Fabrication of coaxial p-Cu2O/n-ZnO nanowire photodiodes

The authors report the deposition of Cu₂O onto vertically well aligned ZnO nanowires by DC sputtering. The average length, average diameter and density of these VLS-synthesized ZnO nanowires were 1 μm, 100 nm and 23 wires/μm², respectively. With proper sputtering parameters, the deposited Cu₂O could fill the gaps between the ZnO nanowires with good step coverage to form coaxial p-Cu₂O/n-ZnO nanowires with a rectifying current–voltage characteristic. Furthermore, the fabricated coaxial p-Cu₂O/n-ZnO nanowire photodiodes exhibit reasonably large photocurrent-to-dark-current contrast ratio and the fast responses.     

Facile fabrication of Zn/Zn5(OH)8Cl2·H2O flower-like nanostructure on the surface of Zn coated with poly (N-methyl pyrrole)

Zn/Zn₅(OH)₈Cl₂·H₂O flower-like nanostructures was electrodeposited on the coated Zn with poly (N-methyl pyrrole) in 0.1 M Zn (NO₃)₂ and 0.1 M KCl solution. The morphology and the structure of the Zn/Zn₅(OH)₈Cl₂·H₂O were characterized by Field Emission Scanning Electron Microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction analysis (XRD). The FT-IR results showed special peaks at 908 and 728 cm⁻¹ related to Zn₅(OH)₈Cl₂·H₂O. The FESEM results indicated that Zn/Zn₅(OH)₈Cl₂·H₂O consists of a flower-like nanostructure and these flower-shaped structures contain many shaped nanopetals with the thickness of 27.8 nm. The XRD result confirmed that the major phase of electrodeposited product in 0.1 M KCl as supporting electrolyte was Zn₅(OH)₈Cl₂·H₂O. The ability of PMPy to create a thin film and the existence of several pores in its matrix act as a mold for the growth of Zn/Zn₅(OH)₈Cl₂·H₂O flower-like nanostructure. The trapping of Cl⁻ and OH⁻ within pores can be considered as the reason for the formation of flowerlike Zn/Zn₅(OH)₈Cl₂·H₂O nanostructures in 0.1 M KCl.     

H2 分子在Li3N(110)表面吸附的第一性原理研究

采用第一性原理方法研究了H₂分子在Li₃N(110)晶面的表面吸附. 通过研究H₂/Li₃N(110)体系的吸附位置、吸附能和电子结构发现: H₂分子吸附在N桥位要比吸附在其他位置稳定,此时在Li₃N(110)面形成两个-NH基,其吸附能为1.909 eV,属于强化学吸附;H₂与Li₃N(110)面的相互作用主要是H 1s轨道与N 关键词： 第一性原理 3N(110)')" href="#">Li₃N(110) 2')" href="#">H₂ 吸附和解离     

Conductivity and water uptake of Sr4(Sr2Nb2)O11·nH2O and Sr4(Sr2Ta2)O11·nH2O

The hydrated oxygen deficient complex perovskite-related materials Sr₄(Sr₂Nb₂)O₁₁·nH₂O and Sr₄(Sr₂Ta₂)O₁₁·nH₂O were studied at high water vapour pressures over a large temperature range by electrical conductivity measurements, thermogravimetry (TG), and X-ray powder diffraction (XRPD). In humid atmospheres both materials are known to exhibit protonic conductivity below dehydration temperatures, with peak-shaped maxima at about 500 °C. In this work we show that the peaks expand to plateaus of high conductivity from 500 to 700 °C at a water vapour pressure of 1 atm. However, in situ synchrotron XRPD of Sr₄(Sr₂Nb₂)O₁₁·nH₂O as a function of temperature shows that these observations are in fact coincident with melting and dehydration of a secondary phase Sr(OH)₂. The stability of Sr₄(Sr₂Nb₂)O₁₁·nH₂O and Sr₄(Sr₂Ta₂)O₁₁·nH₂O in humid atmospheres is thus insufficient, causing decomposition into perovskites with lower Sr content and SrO/Sr(OH)₂ secondary phases. This, in turn, rationalizes the observation of peaks and plateaus in the conductivity of these materials.     

Theoretical investigation of ESR spectra and local structure for VO in Ba2Zn(HCOO)6(H2O)

The electron spin resonance spectra (characterized by g factors g_, g_⊥ and hyperfine structure constants A_ and A_⊥) of Ba₂Zn(HCOO)₆(H₂O) (BZFA): VO²⁺ crystal are calculated from high order perturbation formulas. The calculated results are in good agreement with the observed values. The local structure parameters of [VO(H₂O)₅]²⁺ clusters are also obtained from the calculation. The magnitudes of the metal-ligand distances parallel and perpendicular to the C₄-axis are, respectively, R_≈0.163 nm and R_⊥≈0.210 nm. It is shown that the local structure around the V⁴⁺ ion possesses a compressed tetragonal distortion along C₄-axis.     

H2在MgO团簇吸附的从头计算研究

根据最稳定幻数MgO团簇的结构特点,对H₂在岩盐和管状结构(MgO)_9,12表面的吸附性质进行了从头计算研究.结果表明H₂可以在处于团簇不同位置的Mg正离子或氧负离子上发生物理吸附;在Mg离子上H₂以侧位方式吸附并向Mg转移电子,在O离子上H₂以端位方式吸附并被明显极化.吸附的稳定性主要依赖于吸附离子的位置即配位数,Mg/O离子的配位数越低则吸附越强;在配位数相同时,H₂在M 关键词： 团簇 MgO 2吸附')" href="#">H₂吸附 DFT     

Measurements of positions, strengths and self-broadened widths of H2O from 2900 to 8000 cm: line strength analysis of the 2nd triad bands

High-resolution spectra of H₂O were recorded with a Fourier-transform spectrometer covering H₂O transitions from 2900 to 8000 cm⁻¹. Over 13,000 absorptions were measured to determine line positions, strengths and self-broadened half-width coefficients. The H₂ ¹⁶O line strengths of the (0 3 0)-(0 1 0), (1 1 0)-(0 1 0), (0 1 1)-(0 1 0) and (0 3 0)-(0 0 0), (1 1 0)-(0 0 0), (0 1 1)-(0 0 0) bands were fitted to a quantum mechanical model which involves the interactions between the (0 3 0), (1 1 0), and (0 1 1) vibrational states. Also fitted were experimental strengths of the hot bands; (1 2 0)-(0 1 0) and (0 2 1)-(0 1 0). The model includes 14 dipole matrix elements for B- and A-type transitions. The measured line positions were used along with hot water emission measurements (for the (0 3 0), (0 4 0), and (0 5 0) states of H₂ ¹⁶O) in an analysis to obtain high-accuracy energy level values in the (0 3 0), (1 1 0), (0 1 1), (0 4 0), (1 2 0), (0 2 1), (2 0 0), (1 0 1), (0 0 2), and (0 5 0) vibrational states of H₂ ¹⁶O and the (1 1 0) and (0 1 1) states of H₂ ¹⁷O. Also included were measurements and analysis of self-broadened half-widths for over 4700 absorptions between 4405 and 7729 cm⁻¹. The results from this investigation provide new information for the noted H₂ ¹⁷O bands and present a more accurate representation of the measured H₂ ¹⁶O bands.     

Homogeneous ignition of CH4/air and H2O and CO2-diluted CH4/O2 mixtures over Pt; an experimental and numerical investigation at pressures up to 16 bar

The homogeneous ignition of CH₄/air, CH₄/O₂/H₂O/N₂, and CH₄/O₂/CO₂/N₂ mixtures over platinum was investigated experimentally and numerically at pressures 4 bar p 16 bar, temperatures 1120 K T 1420 K, and fuel-to-oxygen equivalence ratios 0.30 0.40. Experiments have been performed in an optically accessible catalytic channel-flow reactor and included planar laser induced fluorescence (LIF) of the OH radical for the determination of homogeneous (gas-phase) ignition and one-dimensional Raman measurements of major species concentrations across the reactor boundary layer for the assessment of the heterogeneous (catalytic) processes preceding homogeneous ignition. Numerical predictions were carried out with a 2D elliptic CFD code that included elementary heterogeneous and homogeneous chemical reaction schemes and detailed transport. The employed heterogeneous reaction scheme accurately captured the catalytic methane conversion upstream of the gaseous combustion zone. Two well-known gas-phase reaction mechanisms were tested for their capacity to reproduce measured homogeneous ignition characteristics. There were substantial differences in the performance of the two schemes, which were ascribed to their ability to correctly capture the p–T– parameter range of the self-inhibited ignition behavior of methane. Comparisons between measured and predicted homogeneous ignition distances have led to the validation of a gaseous reaction scheme at 6 bar p 16 bar, a pressure range of particular interest to gas-turbine catalytically stabilized combustion (CST) applications. The presence of heterogeneously produced water chemically promoted the onset of homogeneous ignition. Experiments and predictions with CH₄/O₂/H₂O/N₂ mixtures containing 57% per volume H₂O have shown that the validated gaseous scheme was able to capture the chemical impact of water in the induction zone. Experiments with CO₂ addition (30% per volume) were in good agreement with the numerical simulations and have indicated that CO₂ had only a minor chemical impact on homogeneous ignition.