Four-photon polarization spectroscopy of water in a millimeter-wave radiation field

Resonance (frequency 1.4 cm⁽⁻¹) changes induced in the four-photon optical spectrum of water by a millimeter-wave electromagnetic field are observed experimentally. Comparison with the spectrum of ice in the range 0‒2 cm⁽¹ shows that the action of such a field is of a structure-forming character. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 4, 266–268 (25 August 1998)     

Infrared absorption and water structure in aerosol OT reverse micelles

Summary The structure of water in bis(2-ethylhexyl)sodium sulfosuccinate (AOT) micelles has been studied as a function of the [H₂O]/[AOT] ratio (W) by using the absorption IR due to O−H stretching modes in the 3800–3000 cm⁻¹ range. Three systems have been studied: water/AOT/carbon tetrachloride, water/AOT/n-heptane and water/AOT iso-octane. Experimental spectra are presented and discussed for the O−H stretching region both of H₂O and isotopically diluted HDO molecules in D₂O. We have restricted ourselves to the region of small amounts of water (0<W<20) where the properties of the systems change strongly with the water content. The results show that IR spectra can be expressed as sum of contributions from interfacial and bulk-like water. The fraction of water in the two “regions” within the water pool was evaluated as a function ofW. From the data a continuous variation appears in the water properties inside micellar cores rather than a two-steps hydration mechanism. The solubilization of water is described in terms of hydration of the AOT head group and Na⁺ counterions. The maximum hydration number of AOT was found to be 3.5. The same behaviour has been observed in the three solvents studied.     

Collective defect formation in the high-temperature superconductor YBa2Cu3O7 under the influence of adsorbed water molecules

The mechanisms for defect formation stimulated by the adsorption of water molecules in the surface of YBa₂Cu₃O₇ ceramic are studied, together with the types of defects and their distributions. It is found that a water layer physically bound to the surface reduces the rates of annihilation and capture of positrons, changes the amount of barium and copper on the surface by a factor of two, and inhibits diffusive jumps of nickel atoms. A layer of adsorbed water excites subthreshold formation of 10²¹ cm⁻³ interstitial Ba and Cu1 atoms and transitions of oxygen from O1 to O5, and vice versa in the volume of crystallites, and the migration of defects and accumulation of Ba atoms in the surface layer, which block diffusive jumps of Ni within the volume of the crystals. These effects are related to the excitation of collective, low-frequency weakly damped motion of heavy holes in the crystal volume when defects are formed on the surface by physically adsorbed H₂O molecules, which is accompanied by Coulomb repulsion of cations from intermediate layers into interstitials and the migration of defects in the field of the collective excitations. Zh. éksp. Teor. Fiz. 116, 586–603 (August 1999)     

Condensed water in superfluid He-II

It was found that when ⁴He gas containing water vapor as an impurity condenses on the surface of superfluid He-II cooled to ∼ 1.4 K, semitransparent clouds (icebergs) form in the volume of a glass cell filled with He-II below the He-II surface. The form of the icebergs extracted from the superfluid liquid remains virtually unchanged on heating up to ∼ 1.8 K. In the temperature range 1.8–2.2 K the thermometers register sharp temperature jumps, which are accompanied by jumps in the gas pressure in the cell and a repeated decrease, by more than two orders of magnitude, in the total volume of the condensate, i.e., the water content in the volume of an iceberg does not exceed 10²⁰H₂O molecules per 1 cm³. It can be inferred that porous icebergs, permeated with superfluid liquid and containing cores consisting of small clusters surrounded by a layer of solidified helium, form in the volume of He-II as the gas mixture condenses. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 11, 744–748 (10 December 1999)     

Near-infrared diode laser absorption sensor for rapid measurements of temperature and water vapor in a shock tube

A fast-response (100 kHz) tunable diode laser absorption sensor is developed for measurements of temperature and H₂O concentration in shock tubes, e.g. for studies of combustion chemistry. Gas temperature is determined from the ratio of fixed-wavelength laser absorption of two H₂O transitions near 7185.60 cm^-1 and 7154.35 cm^-1, which are selected using design rules for the target temperature range of 1000–2000 K and pressure range of 1–2 atm. Wavelength modulation spectroscopy is employed with second-harmonic detection (WMS-2f) to improve the sensor sensitivity and accuracy. Normalization of the second-harmonic signal by the first-harmonic signal is used to remove the need for calibration and minimize interference from emission, scattering, beam steering, and window fouling. The laser modulation depth for each H₂O transition is optimized to maximize the WMS-2f signal for the target test conditions. The WMS-2f sensor is first validated in mixtures of H₂O and Ar in a heated cell for the temperature range of 500–1200 K (P=1 atm), yielding an accuracy of 1.9% for temperature and 1.4% for H₂O concentration measurements. Shock wave tests with non-reactive H₂O–Ar mixtures are then conducted to demonstrate the sensor accuracy (1.5% for temperature and 1.4% for H₂O concentration) and response time at higher temperatures (1200–1700 K, P=1.3–1.6 atm). PACS 42.62.Fi; 42.55.Px; 42.60.Fc; 07.35.+k     

Study of ion–solvent interactions and activation energy of LiBr in DMSO,H<Subscript>2</Subscript>O and DMSO–H<Subscript>2</Subscript>O mixtures at various temperatures

The Jones–Dole B coefficients of the electrolyte Lithium bromide (LiBr), reference salts tetra butyl ammonium tetra phenyl borate (BU₄NBPh₄), tetra butyl ammonium bromide (BU₄NBr), and potassium chloride (KCl) in dimethylsulfoxide (DMSO), water, and DMSO–water mixtures were obtained at different temperatures range from 25 to 45 °C For this, the relative viscosities were measured for Lithium bromide (LiBr) and reference salts in DMSO, water, and DMSO–water mixtures at above-mentioned temperatures. The B coefficients of these electrolytes were behaved as structure makers in DMSO, while in H₂O and DMSO–H₂O mixtures, the B-coefficient values were less positive showing the weak structure-making effect. Ionic viscosity B coefficients allow us to assess the behavior of ions in the solvent mixtures. In this study it was observed that all the values of ionic B coefficient of (Li⁺) were positive and small showing the weak structure-making effects. It was also observed that Br⁻ ions maintain negative B coefficient values in all DMSO–H₂O mixtures, except in 60% DMSO mole fraction. From this it can be concluded that Br⁻ ion behaved as a structure breaker in water and in all DMSO–H₂O mixtures except in 60% DMSO mole fraction mixtures. The low B _± values of alkali metal ions and Br⁻ ions in water are due to the breakdown of the tetrahedral structural of water and the formation of strongly structured solvated ion. It is also observed that the values of the energy of activation of the flow for LiBr are greater in DMSO–water mixtures and in pure water than in DMSO. This may be due the presence of a network of hydrogen bonds which cause the hindrance in the flow of the solution of LiBr in DMSO–water mixtures and in pure water than in DMSO.     

Isotope effect in the vibrational spectra of water measured in experiments with a scanning tunneling microscope

The vibrational frequencies of adsorbed H₂O and D₂O molecules are measured under high-vacuum conditions by in-cavity scanning tunneling spectroscopy. An isotope effect is observed. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 1, 37–39 (10 July 1997)     

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.     

Synthesis, characterization, DNA binding and cleavage studies of mixed-ligand Cu(II) complexes of 2,6-bis(benzimidazol-2-yl)pyridine

Four novel copper(II) complexes of the composition [CuLX] where L = 2,6-bis(benzimidazole-2yl)pyridine, X = dipyridophenazine (L₁), 1,10-phenanthroline (L₂), hydroxyproline (L₃) and 2,6-pyridine dicarboxylic acid (L₄) were synthesized and characterized by using elemental analysis, FT-IR, UV–vis, ESI-MS, molar conductance and magnetic susceptibility measurements. The complexes [CuLL₁](NO₃)₂ [1], [CuLL₂](NO₃)₂ [2], [CuLL₃](NO₃) [3] and [CuLL₄] (NO₃) [4] are stable at room temperature. In DMSO the complexes [1] and [2] are 1:2 electrolytes, [3] and [4] are 1:1 electrolytes. Based on elemental and spectral studies five coordinated geometry is assigned to all the four complexes. The interaction of four copper ion complexes with calf thymus DNA were carried out by UV–vis titrations, fluorescence spectroscopy, thermal melting and viscosity measurements .The binding constant (K_b) of the above four metal complexes were determined as 5.43 × 10⁴ M_,⁻¹ 2.56 × 10⁴ M⁻¹, 1.21 × 10⁴ M⁻¹ and 1.57 × 10⁴ M⁻¹ respectively. Quenching studies of the four complexes indicates that these complexes strongly bind to DNA, out of all complex 1 is binding more strongly. Viscosity measurements indicate the binding mode of complexes with CT DNA by intercalation through groove. Thermal melting studies also support intercalative binding. The nuclease activity of the above metal complexes shows that 1, 2 and 3 complexes cleave DNA through redox chemistry.     

Magnetic and electrical properties of Mg1−x CuxO solid solutions and magnetic shielding in Cu-Mg1−x CuxO structures

Mg_1−x Cu_xO solid solutions having an NaCl structure with 0⩽x⩽0.20 are synthesized and Cu-Mg_1−x Cu_xO structures are prepared for superconductivity studies. The magnetic susceptibility χ, electron paramagnetic resonance (EPR), and electrical conductivity of the solid solutions are studied at temperatures of 5–550 K. It is shown that χ ⁻¹(T) obeys the Curie-Weiss law with a paramagnetic Curie temperature Θ close to zero and an effective magnetic moment μ _eff=1.9 μ _B, close to the 1.73 μ _B of a Cu²⁺ ion with spin S=1/2. The width ΔH of the EPR line depends weakly on temperature and increases as x is raised. The volume narrowing of the EPR linewidth ΔH is used to estimate the exchange interaction parameter, 3×10⁻⁴ eV. The g-factor is close to 2 and is temperature independent. The electrical conductivity of Mg_1−x Cu_xO at T=300 K is ≈10⁻¹¹–10⁻¹² Ω⁻¹ cm⁻¹ for x=0 and increases to 10⁻⁵–10⁻⁶ Ω⁻¹ cm⁻¹ for x=0.15–0.20. The conductivity is p-type. Magnetic shielding is observed in Cu-Mg_1−x Cu_xO structures with x=0.15 and 0.20. The possible connection of this phenomenon with interference superconductivity in the contact layer of the structure is discussed. Fiz. Tverd. Tela (St. Petersburg) 41, 293–296 (February 1999)     

Gas-phase photoreactions of anthracene, 2-aminoanthracene,and pyrene with oxygen and water vapors

Excited singlet (S ₁) and triplet (T ₁) state quenching by O₂ and by (O₂ + H₂O) gas-vapor mixtures was studied in the gas phase for polycyclic aromatic hydrocarbons (PAHs, anthracene, 2-aminoanthracene, pyrene). Addition of water vapor is shown not to influence quenching of both fluorescence and delayed fluorescence of PAHs by oxygen. The role of complexes stabilized by charge transfer and hydrogen bonds in quenching the excited states of PAHs by atmospheric gases was analyzed. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 342–348, May–June, 2009.     

Possibility of mechanically stimulated transmutation of carbon nuclei in ultradisperse deuterium-containing media

The variation of the concentration of ¹⁴C in graphite subjected to vibratory milling in the presence of heavy (or light) water is investigated using methods of radiocarbon β-spectral analysis. It is discovered that the C+D₂O system exhibits a statistically significant increase in the β counting rate in comparison to the C+H₂O system milled under similar conditions. A quantitative model of the transmutation of the ¹³C isotope into the ¹⁴C isotope involving an interaction of multiphonon excitations with deuterons in the graphite crystal lattice in the presence of background thermal neutrons is proposed. Zh. Tekh. Fiz. 67, 100–107 (June 1997)     

Coincidence of rotational energy of H<Subscript>2</Subscript>O ortho-para molecules and translation energy near specific temperatures in water and ice

A hypothesis of the quantum nature of the specific temperatures T _s of water and ice, whose values is not random, was formulated. It was found that the quantum energy hΩ _mn of closely located rotational transitions in the ortho and para spin isomers of H₂O molecules coincides with the translation energy kT near the well-known specific temperatures T _s in ice and water. On the basis of this fact it was suggested that ortho-para conversion occurs at temperatures close to T _s upon inelastic collisions and resonance energy exchange kT _s ↔ hΩ _mn in the rotation-translation-rotation (RTR) processes. Such conversion can induce rearrangement of the H-bond set structure and repacking of H₂O molecules. The coincidence kT _s ≈ hΩ _mn was checked for ice and water at 12 known T _s, as well as for heavy water D₂O near T _s = 11.2°C (maximum density) and −140°C (glassy transition). The previously observe strong deformation of the OH Raman band near T _s = 4, 19, 36, and 76°C (maximum density, maximum surface tension, minimum heat capacity, and maximum speed of sound, respectively) was interpreted as a manifestation of the water structure rearrangement induced by H₂O ortho-para conversion.     

Electronic and electronic-vibrational phenomena in the new organic conductor ϰ-(ET)2[Hg(SCN)2Cl] with a metal-insulator transition

The reflection spectra and optical conductivity spectra of the new organic conductor ϰ-(ET)₂[Hg(SCN)₂Cl] with a metal-insulator transition in the spectral regions 700–5500 and 9000–40 000 cm⁻¹ have been studied in polarized light at 300 K. A comparisonis made between the spectra obtained and the corresponding spectra of related isostructural conductors based on the ET molecule, and also the properties of the crystal structure of the investigated compounds. An electronic transition between the ET molecules of the dimer (ET) ₂ ⁺ in the spectral region 700–5500 cm⁻¹ has been identified, as have the features of the electronic-vibrational structure arising as a consequence of the interaction of this transition with the completely symmetric intramolecular vibrations of the ET molecule. It is found that the conductor with the stronger dimer interaction between the ET molecules has the higher the transition temperature. Fiz. Tverd. Tela (St. Petersburg) 39, 1313–1319 (August 1997)     

Microhydration of the methylene blue cation in an electrospray ion source

Microhydrated methylene blue cations, MB⁺(H₂O) _n , are produced in an electrospray ion source and their size-distributions are measured as a function of the source temperature. A series of MB⁺(H₂O) _n ions is observed up to n ≃ 60. A striking feature observed in the mass spectra is that the series of hydrated ions starts at n = 4; intensities of n = 1–3 are extremely suppressed. The absence of n = 1–3 ions is well explained by the energetics concerning evaporation processes of water molecules, based on stable structures and the binding energies of MB⁺(H₂O) _n ions calculated by DFT calculations up to n = 5. MB⁺(H₂O) _n ions for n > 4 evaporate a single water molecule sequentially, while MB⁺(H₂O)₄ tends to fragment into MB⁺ and (H₂O)₄ rather than MB⁺(H₂O)₃ and an H₂O molecule. We have observed a clear magic peak at n = 24, which strongly suggests that the MB⁺(H₂O)₂₄ ion is formed by attaching a neutral (H₂O)₂₀ cage onto an MB⁺(H₂O)₄ ion.     

Quantum and semiclassical oscillations in the organic metal (BEDO-TTF)2Clx(H2O)y

We study quantum (Shubnikov-de Haas and de Haas-van Alphen) oscillations and angular oscillations of the reluctance in the organic quasi-two-dimensional metal (BO)₂Cl_x(H₂O)_y. We show that the Fermi surface in this compound consists of a slightly corrugated cylinder with its axis perpendicular to the conducting plane. The cross section of the cylinder in this plane is a perfect circle of radius k _F≃3×10⁷ cm⁻¹. The effective carrier mass associated with this cylinder is m*=(1.65–2.0) m ₀ in the conducting plane, while the Dingle temperature is T _D=3–4 K. Zh. éksp. Teor. Fiz. 114, 1137–1146 (September 1998)     

Fluctuating Electric Field Gradients at 111Cd in Ice

¹¹¹Cd–PAC measurements have been made using the high specific activity of ¹¹¹In in the methanol–water mixtures of various concentrations at the room temperature. These experiments revealed that the perturbation factors 〈A ₂ G ₂〉 (integrated over two mean lives τ_N) do not follow the dependence of the macroscopic viscosity η. The observed dynamic character of the PAC spectra in ice is explained by the mobility of orientational and ionic defects. The activation energy for the diffusion process was determined to be E _a =0.35(1) eV. This revised version was published online in September 2006 with corrections to the Cover Date.     

Synthesis, Characterization, DNA-Binding and Antiproliferative Activity of Nd(III) Complexes With N-(Nitrogen Heterocyclic) Norcantharidin Acylamide Acid

Three novel complexes [Nd(L)(NO₃)(H₂O)₂]·NO₃·2H₂O (HL¹ = N-pyrimidine norcantharidin acylamide acid, C₁₂H₁₃N₃O₄; HL² = N-pyridine norcantharidin acylamide acid, C₁₃H₁₄N₂O₄; HL³ = N-phenyl norcantharidin acylamide acid, C₁₄H₁₅NO₄) were synthesized. HL¹, HL² and HL³ are the ligand of complex(1), complex(2) and complex(3), respectively. Their structures were characterized by elemental analysis, conductivity measurement, infrared spectra and thermogravimetric analysis. The DNA-binding properties of the complexes have been investigated by fluorescence spectroscopy and viscosity measurements. The results suggest that the complexes can bind to DNA by partial intercalation. The liner Stern-Volmer quenching constant K_sq values are 3.3(±0.21)(1), 1.7(±0.19)(2) and 0.9(±0.04)(3), respectively. Complex (1) and (2) have been found to cleave pBR322 plasmid DNA at physiological pH and temperature. The test of antiproliferation activity indicates that complex(1) has strong antiproliferative ability against the SMMC7721 (IC₅₀ = 131.7 ± 23.4 μmol·L⁻¹) and A549 (IC₅₀ = 128.4 ± 19.9 μmol·L⁻¹) cell lines. The inhibition rates of complex(2) (IC₅₀ = 86.3 ± 11.3 μmol·L⁻¹) are much higher than that of NCTD (IC₅₀ = 115.5 ± 9.5 μmol·L⁻¹) and HL² (111.0 ± 5.7 μmol·L⁻¹) against SMMC7721 cell lines.     

Photoinduced self-limited low-temperature growth of ultra-thin silicon-oxide films with water vapor

The growth of ultra-thin (<2 nm) silicon-oxide films was investigated on Si(100):H, Si(111):H, and a-Si:H surfaces in a pure water atmosphere (0.1–10 Pa) at low temperatures of 30–250 °C. Oxidation was induced photochemically by pulsed F₂-laser radiation at 157 nm. The thickness and composition of the growing oxide films were monitored in real time by spectroscopic ellipsometry in the photon energy range of 1.15–4.75 eV. The mechanism of laser-induced silicon oxidation in a H₂O atmosphere is shown to differ fundamentally from the classical Deal–Grove mechanism of thermal oxidation at 900–1200 °C, as well as from the photoinduced low-temperature oxidation in an O₂ atmosphere. In particular, the film thickness essentially does not depend on temperature below 250 °C. A kinetic model is developed for low-temperature silicon oxidation in a H₂O atmosphere. According to this model, the growth is limited at small thicknesses by the oxidation reaction and at larger thicknesses by reactions of the diffusing oxidizing species in the oxide layer. Very good agreement is established between this kinetic model and the ellipsometric measurements and the temperature and pressure dependence of the water oxidation process. PACS 82.65.+r; 07.60.Fs; 81.65.Mq; 82.50.Hp     

Infrared spectra of BeSO4.4H2O and its deuterated analogue in 4000–1200 cm−1 region

IR spectra of BeSO₄.4H₂O and its deuterated analogue at ∼300 K and ∼110 K are reported in the region 4000–1200 cm⁻¹ using thin film and nujol mull techniques. The observed bands have been assigned as the internal modes of the water and the overtones and combinations of various modes using the recently revised assignments of SO₄ ²⁻ and Be(aq)₄ fundamentals in the region 1200–250 cm⁻¹ (Srivastavaet al 1976). The splitting of the internal modes of water has been discussed in the light of the effects of deuteration and cooling and it is shown that all the water molecules in a unit cell are asymmetric but crystallographically equivalent.