Influence of additional metal ions on the ratio of conversion rates of intermediate products of the hydrolysis of adenosine-5′-triphosphoric acid catalyzed by the Cu2+ ion: 1. Experimental study of the influence of Mg2+ ions in the ascending branch of the dependence of the initial hydrolysis rate on pH

The hydrolysis of the dimeric complex (CuATP^2?)₂ to CuADP^? and inorganic phosphate P _i is irreversible. The main intermediate hydrolysis product, whose formation should be taken into account at relatively early steps of hydrolysis, is the pentacovalent intermediate IntK formed in parallel with the hydrolysis to CuADP^? and P _i through the common intermediate product (CuATP^2?)₂OH^? (DOH^?) in step 1, which is the replacement of the nucleophile (OH^?) at the Cu²⁺ ion by OH^? at the positively charged phosphorus atom. The influence of the addition of Mg²⁺ ions is studied (depending on their concentration) on the rate constants of step 1 in the region of pH in the ascending branch of the dependence of the initial hydrolysis rate on pH at two values of pH: 6.48 and 6.70. This region of pH is sensitive to both the rate constant of DOH^? formation and the rate constants of step 1. The rate constant for the formation of DOH^? from D remains unchanged. An increase in the concentration of Mg²⁺ decreases the value of ATP conversion, above which the stationary hydrolysis regime is observed. The ratio [IntK]/[DOH^?] is higher when the stationary regime is attained. The applicability of the method proposed for the formation of the attacking nucleophile and the proposed sequence of steps to the enzymatic phosphoryl transfer processes is discussed.     

Influence of additional metal ions on the ratio of the rates of intermediate product transformations in the hydrolysis of adenizine-5′-triphosphoric acid catalyzed by divalent Cu ions

It was shown earlier that the hydrolysis of the (CuATP²⁻)₂ dimeric complex to CuADP⁻ and inorganic phosphate P _i was an irreversible reaction. The main intermediate hydrolysis product, the formation of which should be taken into account at comparatively early hydrolysis stages, was the IntK pentacovalent intermediate. It was formed in parallel with hydrolysis to CuADP⁻ and P _i through the common intermediate product (CuATP²⁻)₂OH⁻ — DOH⁻. We studied the influence of the addition of various concentrations of Mg²⁺ ions to the reaction mixture at pH 7.1–7.2, a range for which the kinetics of hydrolysis is sensitive to the rate constants of deactivation of DOH⁻ active centers (conjugated with CuADP⁻ formation and occurring via the formation of IntK). The conversion of ATP above which stationary hydrolysis regime was observed decreased as the concentration of Mg²⁺ grew. The DOH⁻ $ \underset{{OH^ - }}{\overset{{OH^ - }}{\longleftrightarrow}}$ \underset{{OH^ - }}{\overset{{OH^ - }}{\longleftrightarrow}} IntK equilibrium according to the conversion of ATP was established more rapidly, and it was to a greater extent shifted toward IntK. It was assumed that hydrated Mg²⁺ linked as a second metal ion with ATP β and γ phosphate groups hydrated IntK much stronger than DOH⁻. The Cu · OH₂ · AMP complex played the role of a common acid catalyst and hydrated DOH⁻ better than Mg²⁺ · OH₂. The selective hydration of DOH⁻ by the CuOH₂ · AMP complex at early hydrolysis stages directed the process toward the formation of IntK, which caused the appearance of an induction period in the formation of CuADP⁻.     

Discussion on the dissociation of fast HD+2 ions traversing thin foils

the discussion is on the following experimental results: The energy distribution of the H+ and D+ fragments resulting from the dissociation of HD+2 molecular ions at energy 1.497 7 MeV has been measured using the Coulomb explosion technique. The spectra were used to determine the binding energy of HD+2 and its structure. There existed differences between the spectral structures for proton and for deuteron.     

Electron spin relaxation of exchange coupled pairs of transition metal ions in solids. Ti2+–Ti2+ pairs and single Ti2+ ions in SrF2 crystals

EPR (X- and Q-band) and electron spin relaxation measured by electron spin echo method (X-band) were studied for ${\text{Ti}}^{2+}(S=1)$ and ${\text{Ti}}^{2+}''–''{\text{Ti}}^{2+}$ pairs in ${\text{SrF}}_2$ crystal at room temperature and in the temperature range 4.2–115 K. EPR spectrum consists of a strong line from ${\text{Ti}}^{2+}$ and quartets 2:3:3:2 from titanium pairs $(S=2)$. Spin-Hamiltonian parameters of the pairs are $g_{\parallel }=1.883$, $g_{\perp }=1.975$ and $D=0.036{\text{cm}}^{-1}$. Temperature behavior of the dimer spectrum indicates ferromagnetic coupling between ${\text{Ti}}^{2+}$. Spin–lattice relaxation of individuals ${\text{Ti}}^{2+}$ is dominated by the ordinary two-phonon Raman process involving the whole phonon spectrum up to the Debye temperature ${\Theta }_{\text{D}}=380\text{K}$ with spin–phonon coupling parameter equal to $215{\text{cm}}^{-1}$. Important contribution to the relaxation arises from local mode vibrations of energy $133{\text{cm}}^{-1}$. The pair relaxation is faster due to the exchange coupling modulation mechanism with the relaxation rate characteristic for ferromagnetic ground state of the pairs $1/T_1\propto [\exp (2J/\mathit{kT})-1{]}^{-1}$ which allowed to estimate the exchange coupling $J=36{\text{cm}}^{-1}$. The theories of electron–lattice relaxation governed by exchange interaction are outlined for extended spin systems, for clusters and for individual dimers. Electron spin echo decay is strongly modulated by coupling with surrounding ¹⁹F nuclei. FT-spectrum of the modulations shows a dipolar splitting of the fluorine lines, which allows the evaluation of the off-center shift of ${\text{Ti}}^{2+}$ in pair as 0.132 nm. The electron spin echo dephasing is dominated by an instantaneous diffusion at low temperatures and by the spin–lattice relaxation processes above 18 K.     

The H—H+, H+—H+ and H—H fragmentation in the collision-induced dissociation of H 2 + ions

The collision-induced dissociation of 10 keV H ₂ ⁺ ions incident on H₂ has been studied in this paper. Total cross sections and angle distributions for the H⁺-H, H⁺-H⁺ and H-H fragmentations are given. Distributions over both angle and velocity have been measured for the H-H⁺ and H-H fragmentation.     

Synthesis and optical properties of Co2+ and Ni2+ ions doped β-BaB2O4 nanopowders

Co²⁺ and Ni²⁺ ions doped β-BaB₂O₄ nanopowders have been prepared by co-precipitation method and their structural properties are studied by spectroscopic techniques. Powder XRD data reveals that the crystal structure belongs to monoclinic and the average crystallite size is calculated. Optical absorption spectra data reveal octahedral site symmetry for Co²⁺ and Ni²⁺ ions. Crystal field (Dq) and inter-electron repulsion (B and C) parameters are evaluated for Co²⁺ doped β-BaB₂O₄ nanopowders as Dq=960, B=900 and C=3850 cm^?1 and for Ni²⁺ doped β-BaB₂O₄ nanopowders, Dq=900, B=850 and C=3500 cm^?1. FT-IR spectra showed the characteristic vibrational bands related to BO₃ and BO₄ molecules. Photoluminescence spectra contain the emission bands in ultraviolet and blue regions.     

Spin-spin interaction of Ni2+ ions in ZnSiF6·6H2O

The angular dependences of the electron spin resonance spectrum of 1% Ni²⁺ ions in a ZnSiF₆·6H₂O matrix are investigated experimentally at 36 GHz and 4.2 K. Besides the main spectrum of the isolated ion, we observed a spectrum due to interacting pairs of Ni²⁺ ions, located in the first (nn) and second (2n) coordination spheres and coupled by, besides the magnetic dipole-dipole interaction, isotropic exchange: J _nn = (−197±1)×10⁻⁴, J _2nα = (−5±1)×10⁻⁴, and J _2nβ = (3±2)×10⁻⁴ cm⁻¹. Lines due to other isolated Ni²⁺ ions, which have a different initial splitting D, are also present in the spectrum with intensity comparable to the pair spectrum. Low-symmetry distortions of the crystal field are observed, caused by a pair of impurity ions located close to one another. It is shown that the previously proposed interpretation is incorrect. Fiz. Tverd. Tela (St. Petersburg) 41, 1602–1608 (September 1999)     

Discussion on the dissociation of fast HD^＋2 ions traversing thin foils

the discussion is on the following experimental results:The energy distribution of the H^ and D^ fragments resulting from the dissociation of HD^ 2 molecular ions at energy 1.4977 MeV has been measured using the Coulomb explosion techoique,The spectra were used to determing the binding energy of HD^ 2 and its structure,There existed differenoes between the spectral structures for proton and for deuteron.     

Rotational Analysis of the B2Σ+-X2Σ+ Bands of 12C18O+

The emission spectrum of the B²Σ⁺-X²Σ⁺ (First Negative) system of the molecular ion ¹²C¹⁸O⁺ have been photographed at a resolution sufficient to observe the spin splitting of the lines with N > 18. Four bands, 0-1, 0-3, 1-4 and 2-5, have been rotationally analyzed and the molecular constants of the B²Σ⁺ , v = 0,1, 2 and X²Σ⁺ , v =1, 3, 4, 5 have been obtained.     

Effect of manganese ions concentration on the anatase–rutile phase transformation of TiO2 films

The phase structures of Ti_1?xMn_xO₂ (0?x<0.08) films synthesized by sol–gel spin coating have been investigated. The effect of Mn dopants on the stability of titanium dioxide (TiO₂) was studied by X-ray diffraction and Raman spectra for isochronally annealed samples. The increased Mn dopant concentration decreased the onset temperature of anatase–rutile (A–R) phase transformation. The calculated activation energy for the phase transformation decreased from 173.6 to 89.4 kJ/mol with Mn dopants concentration increasing from 0% to 7.51%. The Mn ions incorporated into the TiO₂ lattice reduce the rutile nucleation barrier and promote the nucleation rate.     

Study of the ν2 + ν10 Hybrid Band of the Trans-C2H2D2 Molecule

Russian Physics Journal - The ν2 + ν10 (Bu) hybrid band of the trans-C2H2D2 molecule in the region 2100–2300 cm–1 is studied for the first time. The spectrum has been analyzed...     

Rotational Analysis of the 1–4 Band of the B 2Σ+–X 2Σ+ System of 14C16O+

ABSTRACT

High-resolution emission spectrum of the 1–4 band of the B ²Σ⁺–X ²Σ⁺ transition of ¹⁴C¹⁶O⁺ was observed for the first time by conventional emission spectroscopy. The band spectrum was excited in a water-cooled Geissler lamp filled with commercial gaseous carbon monoxide enriched in about 80% of the radiocarbon ¹⁴C. A rotational analysis has been carried out and obtained molecular constants have been merged with previously published data for the B ²Σ⁺–A ²Π_i and A ²Π_i–X ²Σ⁺ transitions. The principal equilibrium constants for the ground X ²Σ⁺ state obtained from this work are ω_e = 2121.7726(98), ω_e x _e = 13.9055(27), B _e = 1.815290(30), α_e = 1.6594(33) × 10^?2, and γ_e = ? 0.377(73) × 10^?4 cm^?1. Also, presently known experimental equilibrium molecular constants of the X ²Σ⁺ states of the CO⁺ isotopic molecules are summarized and isotopic dependence of the B _e and ω _e constants is discussed.     

Surface morphology of MgO (100) crystals implanted with MeV Al+ and Al2+ ions

MgO (100) single crystals are implanted with 1.50-MeV Al⁺ and 3.00-MeV Al₂ ⁺ ions at a fluence of 1×10¹⁵ Al  atoms  cm^-2 under high-vacuum conditions. The surface morphology of the substrate is measured in air using atomic force microscopy and X-ray reflectometry followed by computer-simulated spectrum analysis. The ion-irradiated areas are found to protrude to different heights on the nanometre scale. Small height differences are observed in the areas irradiated by Al⁺ and Al₂ ⁺ ions of comparable energy, dose rate and total fluence. The results indicate that protrusions are most likely caused by implantation-induced point defects (vacancies) generated in the crystal during implantation. Other possibilities for the cause of protrusions are discussed. Thermal treatment stimulates a partial recovery of the implantation damage and alters the topography of MgO surfaces. Received: 22 May 2001 / Accepted: 30 May 2001 / Published online: 25 July 2001     

State selective predissociation spectroscopy of hydrogen chloride ions (HCl+) via the A2Σ+ ← X2Π3/2 transition

The photodissociation of hydrogen chloride ions (HCl⁺) has been investigated through the A²Σ⁺ (ν′ = 6, 7 and 8) ← X ²Π_3/2 (ν″ = 0) transition. The spectra reveal that state selective photodissociation with complete resolution of the spin, orbital, and rotational angular momentum is possible in the A ²Σ⁺ (ν′ = 6) state. The analysis of these spectra yields the rotational and the spin-rotation coupling constant of the A ²Σ⁺ (ν′ = 6) state. The lifetime of HCl⁺ decreases significantly with increasing vibrational excitation in the ²Σ⁺ state. Within the experimental error limits no J dependence of the lifetime is observerd. The state selective photodissociation of the HCl⁺ ions is also shown to be a very sensitive probe for unexpected parity transitions in the 2 + 1 REMPI formation of the HCl⁺ ions in the X 2Π_3/2 (ν″ = 0) state.     

B 2Σ u + excited states of the N + 2 ion and the electron temperature in the discharge afterglow of an Ar-N2 mixture

The electron energy distribution function in the afterglow of a low-pressure discharge in an Ar-N₂ mixture was experimentally found. The values of electron temperature were determined. At the initial stage of plasma decay, the electron temperature was shown to be close to the nitrogen vibrational temperature. A study was made of the afterglow observed in the bands of the first negative system of N ₊ ² , and it is shown that this afterglow may be attributed to collisions of argon ions with nitrogen molecules found on higher vibrational levels.