Proton ENDOR of VO(H2O)5 2+ in Mg(NH4)2(SO4)2)26H2O

ENDOR measurements at 25 K have been used to determine the hyperfine coupling tensors for all ten protons in the VO(H₂O)₅ ²⁺ ion in single crystals of Mg(NH₄)₂(SO₄)₂6H₂O. The traceless components of all the tensors are close to axial and their use in a point dipole treatment enables a very plausible geometrical model of the complex ion to be constructed. Six of the protons in the equatorial water molecules have substantial positive isotropic couplings and it is suggested that these reflect the direct admixture of hydrogen 1s components into the singly occupied orbital.     

Vibrational spectra of Na4P2O7·10H2O

The IR and Raman spectra are measured and analysed for sodium pyrophosphate decahydrate. The spectra are interpreted on the basis of P₂O ₇ ⁴⁻ ion and water vibrations. The observed results fit with the features predicted for the factor goup model. The appearance of two sets of frequencies in the stretching and bending regions of water suggests the existence of two kinds of water molecules in the crystal. This is confirmed by deuterium substitution.     

Infrared spectra and isomeric structures of hydroxide ion-water clusters OH- (H2O)1-5: a comparison with H3O (H2O)1-5

Size-selected hydroxide ion water tetramers and pentamers [OH-(H₂O)_4,5], produced by a supersonic expansion, have been investigated using vibrational predissociation spectroscopy in conjunction with ab initio calculations based on density functional theory (DFT). The observed spectra in the frequency range 2650–3850 cm^?1 show some broad absorption bands attributed to the free and hydrogen bonded OH stretches of OH-(H₂O)_4,5 at an estimated cluster temperature of 170 K. DFT calculations performed at the B3LYP/6-31 + G* level reveal five and eight possible low lying isomeric forms for OH-(H₂O)₄ and OH-(H₂O)₅, respectively. The global minimum isomer of the tetramer is tri-solvated cyclic, which is energetically more stable than the tetra-solvated wheel-shaped form with an OH- ion at its centre. Compact cage-like lowest energy structures are found for the pentamer, in which the water molecules can act either as a single-donor-single-acceptor, as a double-proton-donor, or as a double-donor-single-acceptor in both the firs1183t a1192nd the second solvation shell of the OH- ion core. Interconversion among the isomers appears to be rapid as manifested in the observed spectra dominated by broad and congested absorptions. To understand the nature of spectral broadening and congestion, systemic comparisons of the results are made against those of the corresponding protonated cations, H+(H₂O)_n|1 and the corresponding halide anions, X-(H²O)ⁿ X = F, Cl, Br, and I. It is suggested that the spectral complexities observed for OH-(H₂O)_4,5 are predominantly a result of sampling configurations with a large distribution of O_solvent-O_ion-O_solvent angles and O_solvent … H-O_solvent distances between water molecules in the firs1175t a1181nd/or second hydration shells, together with the existence of more than one isomer in the supersonic expanson and rapid isomeric interconversion among them.     

Dynamic registration of D2 16O absorption spectrum in silica aerogel

Absorption spectra of the gas phase and adsorbed D₂О in the silica aerogel with nanoscale pores were investigated in 3700–5400 cm^?1 range using dynamic registration with Fourier Transform spectrometer IFS-125M. Two types of sample with pores of 60 nm wide – the nitrogen gas-treated and untreated aerogels – were examined. The surface treatment of the sample changes noticeably the broadband absorption of adsorbed water. Spectrum of D₂O in the pores differs from the spectrum of bulk water as for bandwidth so for band maximum. It was found that treatment of the pores by dry nitrogen leads to increasing hydrophilic properties of the material and to change water band contour. The D₂О line widths in both the aerogels exceed those of free monomer in 1.1–3 times at the same pressure. Calculations of self-broadening coefficients of the D₂O lines were performed using semi-empirical method based on the impact theory of broadening and includes the correction factors. The calculated results well agree with experimental data. Greater differences were found for the shift of the line centre. The D₂O line shifts in the treated pores significantly exceed line shifts in the untreated pores. For some lines, these shifts have the opposite sign indicating complex nature of the molecule–wall interaction.     

Raman microscopy of haidingerite Ca(AsO3OH)·H2O and brassite Mg(AsO3OH)·4H2O

Raman spectroscopy has been used to study the arsenate minerals haidingerite Ca(AsO₃OH)·H₂O and brassite Mg(AsO₃OH)·4H₂O. Intense Raman bands in the haidingerite spectrum observed at 745 and 855 cm⁻¹ are assigned to the (AsO₃OH)²⁻ν₃ antisymmetric stretching and ν₁ symmetric stretching vibrational modes. For brassite, two similarly assigned intense bands are found at 809 and 862 cm⁻¹. The observation of multiple Raman bands in the (AsO₃OH)²⁻ stretching and bending regions suggests that the arsenate tetrahedrons in the crystal structures of both minerals studied are strongly distorted. Broad Raman bands observed at 2842 cm⁻¹ for haidingerite and 3035 cm⁻¹ for brassite indicate strong hydrogen bonding of water molecules in the structure of these minerals. OH···O hydrogen‐bond lengths were calculated from the Raman spectra based on empirical relations. Copyright © 2009 John Wiley & Sons, Ltd.     

SIMS,EID and flash-filament investigation of O2, H2, (O2 + H2) and H2O interaction with vanadium

Comparative investigations of secondary ion emission, electron induced ion emission and flash filament signals from polycrystalline vanadium surfaces exposed to well-defined O₂, H₂, H₂O and (O₂ + H₂) doses (<500 L) have been carried out. The vanadium target could be heated and bombarded by either electrons (300 eV) or ions (3 keV) under ultra high vacuum conditions (<10^?10 Torr). The investigations were carried out with a computer controlled ultra high vacuum mass spectrometer. The experimental results establish exact reproducible spectra of well defined surface layers. They give detailed insight into the reactions between H₂, O₂ H₂O and vanadium, and some interactions between these species. They further indicate the importance of bulk and surface diffusion as well as the influence of the probing ion and electron bombardment. A clear distinction between bulk oxygen, surface oxides, and adsorbed oxygen for the vanadium-oxygen interaction at room temperature could be established. For the interaction of hydrogen with clean and oxygen covered vanadium surfaces the formation of adsorbed hydrogen, bulk solution of hydrogen, and the formation of OH groups and H₂O could be demonstrated. A detection limit below 10^?5 of one single monolayer for metal bonded hydrogen could be established.     

FT-IR Study of the Interaction Between H2O,D2O,HOD, and Pyridines

Abstract

The complexes between H₂O, D₂O, HOD and pyridine have been studied in 1,2-dichloroethane by FT-IR spectrometry. Equal splittings of the stretching bands of H₂O and D₂O about their uncoupled vibrations are observed. The coupling between the asymmetric and symmetric vibrations reaches a value of zero when the band separation is greater than 500 cm^?1 for the OH vibrations and 365 cm^?1 for the OD vibrations. The v_OH stretching frequencies of the HOD ‥ complexes and the v_OD stretching frequencies of the DOH‥ complexes increase by complex formation. These features are explained by an electronic reorganization within the hydrogen bond.     

Die Eigenschwingungen des Metall-Hydratkomplexes in BeSO4·4H2O und BeSO4·4D2O

Infrared reflection spectra of single crystals of BeSO₄·4H₂O and BeSO₄·4D₂O have been obtained in polarized light at 300°K and at 14°K in the region between 4000 cm^?1 and 300 cm^?1. By a Kronig-Kramers analysis, the frequencies of the infrared active transitions have been calculated. These transitions are attributed to internal vibrations of the water molecules and sulfate ions and, in the region between 1000 cm^?1 and 300 cm^?1, especially to internal and external vibrations of the tetrahedral Be⁺⁺·4aqu-complexes. The vibrational modes of these complexes consist of a superposition of translational and librational modes of the water molecules and translational modes of the central Be⁺⁺-ion. The vibrational frequencies and normal modes of this complex have been calculated in a central-force model, and force-constants have been determined by fitting the calculated frequencies to the observed spectra. The calculations have shown that the modes, which comprise mainly translational motions of the water molecules, are strongly coupled with librational motions of the water molecules. On the other hand, there exist pure librational modes with practically no admixture of translational motions. The optimum sets of force constants for the BeSO₄·4H₂O crystal and the BeSO₄·4D₂O crystal differ in a manner which can be understood under the assumption that the dimensions of the Be(D₂O)₄ complex are about 0.1 Å larger than those of the Be(H₂O)₄ complex. Some arguments supporting this conclusion will be discussed.     

Silver-tracer diffusion in Cu2O

The diffusion of¹¹⁰Ag in Cu₂O has been measured by a serial-sectioning technique as a function of temperature (700–1132°C) and oxygen partial pressure (6 × 10^?6 ?8 × 10^?2 atm). The data are fit to the defect model for Cu₂O developed by the authors in the preceding paper. Silver ions have a larger impurity-vacancy binding free energy and/or a larger jump frequency for the singly charged cation vacancies relative to that for the neutral cation vacancies. The activation enthalpies for the diffusion of copper and silver ions in Cu₂O are nearly equal, but the absolute value of D¹_Ag is about three times larger than D¹_Cu even though the silver ion is 31% larger than the copper ion.     

Raman spectroscopic study of the tellurite minerals: graemite CuTeO3·H2O and teineite CuTeO3·2H2O

Tellurites may be subdivided according to formula and structure. There are five groups based upon the formulae (a) A(XO₃), (b) A(XO₃)·xH₂O, (c) A₂(XO₃)₃·xH₂O, (d) A₂(X₂O₅) and (e) A(X₃O₈). Raman spectroscopy has been used to study the tellurite minerals teineite and graemite; both contain water as an essential element of their stability. The tellurite ion should show a maximum of six bands. The free tellurite ion will have C_3v symmetry and four modes, 2A₁ and 2 E. Raman bands for teineite at 739 and 778 cm⁻¹ and for graemite at 768 and 793 cm⁻¹ are assigned to the ν₁ (TeO₃)²⁻ symmetric stretching mode while bands at 667 and 701 cm⁻¹ for teineite and 676 and 708 cm⁻¹ for graemite are attributed to the ν₃ (TeO₃)²⁻ antisymmetric stretching mode. The intense Raman band at 509 cm⁻¹ for both teineite and graemite is assigned to the water librational mode. Raman bands for teineite at 318 and 347 cm⁻¹ are assigned to the (TeO₃)²⁻ν₂(A₁) bending mode and the two bands for teineite at 384 and 458 cm⁻¹ may be assigned to the (TeO₃)²⁻ν₄(E) bending mode. Prominent Raman bands, observed at 2286, 2854, 3040 and 3495 cm⁻¹, are attributed to OH stretching vibrations. The values for these OH stretching vibrations provide hydrogen bond distances of 2.550(6) Å (2341 cm⁻¹), 2.610(3) Å (2796 cm⁻¹) and 2.623(2) Å (2870 cm⁻¹) which are comparatively short for secondary minerals. Copyright © 2008 John Wiley & Sons, Ltd.     

The interaction of CO and O2 with the (111) surface of Pt3Ti

The electronic properties of clean and partly oxidized Pt₃Ti(111) surfaces have been studied utilizing carbon monoxide both as a probe and as a reducing agent. Vibrational frequencies and desorption profiles of chemisorbed CO as well as ion scattering and angular resolved X-ray photoelectron spectroscopy (XPS) suggest that the first atomic layer of annealed Pt₃Ti(111) is quasi-pure platinum. Scarcely any (θ ≈ 0.01) dissociation of CO was observed. Minor shifts of vibrational frequencies and desorption temperatures compared to Pt(111) and a p(2 × 2) “reconstruction” of the clean surface reveal some influence of the bulk. Auger spectroscopy, XPS, and ion scattering all show an increased titanium signal as a result of oxidation. Surface bound atomic oxygen gives a vibrational band around 650 cm⁻¹ which coincides with infrared absorption spectra of TiO₂. Flashing with CO shifts the band to 500 cm⁻¹. Correlated with this shift we observe (i) CO₂ desorption at a temperature well above that observed for Pt(111)/O, (ii) an altered Ti XPS signal, and (iii) a reduced oxygen concentration. Subsequently adsorbed CO molecules vibrate at the same frequencies as on the bare surface, give the same c(4 × 2) LEED pattern, and desorb at the same temperatures but with reduced intensity, in all proving that the surface oxide only acts as a site-blocker with respect to the metal surface. Our current understanding of these observations is that oxygen creates “islands of TiO₂”, segregated to the surface but with no electronic influence on remaining areas of the platinum enriched metal surface. The hexacoordinated Ti⁴⁺ ions on the surface of these islands are reduced by CO to pentacoordinated Ti³⁺ species. The vibrational shift, 650 to 500 cm⁻¹, can be understood by the dipole active bands of a triatomic O−Ti⁴⁺ −O vibrator compared to a diatomic Ti³⁺−O vibrator.     

Incoherent quasielastic neutron scattering from H2O and aqueous ZnCl2 solutions

A study of the diffusive motions of the protons in pure water and ZnCl₂ aqueous solutions has been performed, using incoherent quasielastic neutron scattering. It is shown that it is essential to take into account the rotational motion of the water molecules. The translational linewidth is conveniently fitted over the whole Q-range, using the Random Jump Diffusion model for which the jump length turns out to be roughly the same for pure H₂O and the saturated solution, fairly close to the distance between protons in the water molecule.     

Adsorption of H2O on Al(111)

The adsorption of H₂O on Al(111) has been studied by ESDIAD (electron stimulated desorption ion angular distributions), LEED (low energy electron diffraction), AES (Auger electron spectroscopy) and thermal desorption in the temperature range 80–700 K. At 80 K, H₂O is adsorbed predominantly in molecular form, and the ESDIAD patterns indicate that bonding occurs through the O atom, with the molecular axis tilted away from the surface normal. Some of the H₂O adsorbed at 80 K on clean Al(111) can be desorbed in molecular form, but a considerable fraction dissociates upon heating into OH_ads and hydrogen, which leaves the surface as H₂. Following adsorption of H₂O onto oxygen-precovered Al(111), additional OH_ads is formed upon heating (perhaps via a hydrogen abstraction reaction), and H₂ desorbs at temperatures considerably higher than that seen for H₂O on clean Al(111). The general behavior of H₂O adsorption on clean and oxygen-precovered Al(111) (θ_O ? monolayer) is rather similar at low temperature, but much higher reactivity for dissociative adsorption of H₂O to form OH _adsis noted on the oxygen-dosed surface around room temperature.     

Vibrational Spectra and Structure of Potassium Alum Kal(SO4)2·12[(H2O) x (D2O)1−x ]

The IR spectra and polarization Raman spectra of Kal(SO₄)₂·12(H₂O) and Kal(SO₄)₂·12[H₂O)_0.3(D₂O)_0.7] crystals at 93 K and room temperature have been obtained experimentally. The vibrational spectra of structural elements of potassium alum — the complexes [Al(H₂O)₆ ³⁺ and [Al(D₂O)₆]³⁺ — have been calculated. The vibrational spectra have been interpreted based on the calculation and factor-group analysis data. The spectral data obtained point to the fact that, in the crystals considered, the sulfate ions are partially disordered and there exist two crystallographically different types of water molecules.     

Site of the positive muon in YBa2Cu3O7

A combination of μSR and¹⁷O nuclear quadrupolar μLCR has been used to obtain detailed information on the muon site in YBa₂Cu₃O₇. The rms magnitude of the nuclear dipolar fields in YBa₂Cu₃O₇ enriched with 38%¹⁷O is about twice that in the natural¹⁶O sample. In addition the¹⁷O μLCR spectrum shows that the electric field gradient tensor at the oxygen closest to the muon is almost equal to that measured by NMR for the CuO₂ plane sites O(2,3). These results suggest that the muon in fully oxygenated YBa₂Cu₃O₇ is located at a single site 1.0 Å from an oxygen ion, probably O(2,3).     

Water enrichment by H2O ortho-isomer: Four-photon and NMR spectroscopy

Ratio of H₂O ortho-/para-spin-isomers in water of different treatment procedures (distilled or cavitation fountain) were studied by both Rayleigh wing four-photon spectroscopy and ¹H nuclear magnetic resonance (NMR) spectroscopy. Low-frequency gas-like rotational resonances were observed in the 0.1–1.5 cm^?1 (3–45 GHz) spectral range and NMR proton density was measured in both water samples. We established that the intensity of ortho-isomer line (6₁₆?5₂₃)0.74 cm^?1 measured by four-photon spectroscopy increases by factor of ～3.5 after cavitation treatment of distilled water. Moreover, the proton density measured by NMR spectroscopy in the same sample grows on ～17%. We have suggested that the enrichment of the distilled water by ortho-H₂O molecules was achieved due to cavitation bubbles collapse when the water passes through the supercritical state.     

The assignment of quantum numbers in the theoretical spectra of the H2 16O, H2 17O, and H2 18O molecules calculated by variational methods in the region 0–26000 cm−1

Quantum numbers have been assigned in the theoretical spectra of three isotopologues of the water molecule: H₂ ¹⁶O, H₂ ¹⁷O, and H₂ ¹⁸O. The spectra were calculated by variational methods in the region 0–26000 cm^?1 at a temperature of 296 K. For each molecule, the quantum numbers are assigned to more than 28000 levels. The quantum numbers are assigned to 216766, 210679, and 211073 spectral lines of the H₂ ¹⁶O, H₂ ¹⁷O, H₂ ¹⁸O molecules, respectively. The theoretical spectra with the assigned quantum numbers are available in the Internet.     

Raman spectroscopic study of the arsenite mineral vajdakite [(Mo6+O2)2(H2O)2As3+2O5]·H2O

Raman spectra of vajdakite, [(Mo⁶⁺O₂)₂(H₂O)₂As O₅]·H₂O, were studied and interpreted in terms of the structure of the mineral. The Raman spectra were compared with the published infrared spectrum of vajdakite. The presence of dimolybdenyl and diarsenite units and of hydrogen bonded water molecules was inferred from the Raman spectra which supported the known and published crystal structure of vajdakite. Mo O and O H···O bond lengths were calculated from the Raman spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Adsorption of N2O on Ru(001)

The adsorption of N₂O on Ru(001) at ~ 100K has been studied using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and thermal desorption spectroscopy (TDS). At low exposures, N₂O partly dissociates leaving atomic oxygen on the surface and desorbing N₂. With increasing N₂O exposures, molecular adsorption becomes dominant. He II UPS of the gas phase, solid and monolayer adsorbed molecular N₂O are compared. To within experimental error, the peak spacings in all three are the same. The distributions of intensities in the gas and solid phase spectra are the same. In the monolayer spectra, the 7~σ (terminal nitrogen lone pair) orbital intensity is decreased significantly indicating that it is more strongly coupled to the surface than the other valence orbitals. No molecular N₂O remains after heating to above 180 K and no detectable amount of dissociated nitrogen appears. Molecularly adsorbed N₂O is easily dissociated by an electron beam to give N₂(g), NO(g) and O(a).     

Ultraviolet radiation sources on (H2O,D2O) water vapor

Emission characteristics of ultraviolet (UV) radiation from water vapor (H₂O, D₂O, and a mixture of H₂O and D₂O vapors) excited by pulse-periodic discharges with open electrodes, as well as electrodes outside the discharge tube (capacitive discharge), are presented. Radiation is studied in a spectral range of 175–350 nm. The emission characteristics of a UV radiation source based on vapors of ordinary and “heavy” water, as well as the results of optimization of brightness of radiation bands from the OH and OD radicals as functions of pressure and the composition of the He-H₂O and He-D₂O mixtures, are reported.