On distribution over the cathode surface of the current due to positive ions in discharge with oscillating electrons

The mechanisms of processes determining distribution of positive ions on the cathode surface in a discharge with oscillating electrons are studied. At low pressures P≤5×10⁻⁵ torr over the entire range of anode length variation l _a=0.5–11 cm, the ion current distribution over the cathode radius J _i(r) features a single maximum in the center and drops steeply with distance from the axis. At pressures P=1–4×10⁻⁴ torr, the distribution J _i(r) for short anodes (l _a<6 cm) is similar to the previous one but, for long anodes (l _a=6–10 cm), new maxima at higher J _i values have been detected. A physical explanation for the obtained results is proposed.     

Calculation of the parameters of excimer light sources on the basis of a positive column glow discharge

We calculate the concentration of plasma and gas-temperature components in a contracted filament of a glow capillary discharge (R = 0.75 mm) in xenon for pressures of P = 100 and 400 Torr and currents of I = 6–15 mA for cases of with and without cryogenic cooling of the discharge. We find that the gas temperature in the channel of the glow discharge has a value of 1000–2000 K, the concentration of xenon excimers attains a maximum at the boundary of the filament with a value of 10¹⁰–10¹¹ cm⁻³, and the efficiency of electric energy transformation into excimer radiation energy has a value of 0.1–5%.     

Doppler spectroscopy of a beam in the channel of a H− ion source

It is shown that high-accuracy contact-free measurements of the divergence and emittance of an accelerated H⁻ ion beam at the exit from the source can in principle be performed by passive Doppler spectroscopy of a beam of excited hydrogen atoms produced by neutralization of the ions with excitation on the residual gas in the source channel. The intensity of the H_α-line radiation detected by the Doppler system is calculated, taking into account the principal processes leading to the excitation and deexcitation of the 3s, 3p, and 3d levels of the hydrogen atoms in the beam, for residual gas densities of the order of 10⁻⁴–10⁻⁵ Torr in the source channel. The computed H_α-line intensity was confirmed experimentally, making it possible to perform photoelectronic detection of the spectral contour of the line in the current mode rather than the photon-counting mode. Zh. Tekh. Fiz. 68, 15–18 (June 1998)     

Experimental and computational study of the passage of an electron beam through the curvilinear element of the Drakon stellarator system in a tenuous plasma

Results are presented from the first stage of studies on the passage of an electron beam with energy 100–500 eV in a magnetic field of 300–700 Oe through the curvilinear solenoid of the KRéL unit, the latter being a prototype of the closing segment of the Drakon stellarator system, in the plasma-beam discharge regime. The ion density at the end of the curvilinear part of the chamber, n _i ≈8×10⁸–10¹⁰ cm⁻³, the electron temperature T _e ≈4–15 eV, and the positions at which the beam hits the target for different distances from it to the electron source are determined experimentally. The motion of the electron beam is computationally modeled with allowance for the space charge created by the beam and the secondary plasma. From a comparison of the experimentally measured trajectories and trajectories calculated for different values of the space charge, we have obtained an estimate for the unneutralized ion density of the order of 5×10⁷ cm⁻³. Zh. Tekh. Fiz. 69, 22–26 (February 1999)     

Pulsed laser deposition of Zr–N codoped <Emphasis Type="Italic">p</Emphasis>-type ZnO thin films

Present p-type ZnO films tend to exhibit high resistivity and low carrier concentration, and they revert to their natural n-type state within days after deposition. One approach to grow higher quality p-type ZnO is by codoping the ZnO during growth. This article describes recent results from the growth and characterization of Zr–N codoped p-type ZnO thin films by pulsed laser deposition (PLD) on (0001) sapphire substrates. For this work, both N-doped and Zr–N codoped p-type ZnO films were grown for comparison purposes at substrate temperatures ranging between 400 to 700 °C and N₂O background pressures between 10⁻⁵ to 10⁻² Torr. The carrier type and conduction were found to be very sensitive to substrate temperature and N₂O deposition pressure. P-type conduction was observed for films grown at pressures between 10⁻³ to 10⁻² Torr. The Zr–N codoped ZnO films grown at 550 °C in 1×10⁻³ Torr of N₂O show p-type conduction behavior with a very low resistivity of 0.89 Ω-cm, a carrier concentration of 5.0×10¹⁸ cm⁻³, and a Hall mobility of 1.4 cm² V⁻¹ s⁻¹. The structure, morphology and optical properties were also evaluated for both N-doped and Zr–N codoped ZnO films.     

Solid Substrate–Room Temperature Phosphorimetry for the Determination of Trace Terbutaline Sulfate Based on Its Inhibition Oxidation of Rhodamine 6G by Sodium Periodate

When 1.00 mol l⁻¹ I⁻ is used as ion perturber, rhodamine 6G (Rh 6G) can emit strong and stable room temperature phosphorescence (RTP) on filter paper substrate in KHC₈H₄O₄–HCl buffer solution (pH = 3.50), heated at 70 °C for 10 min. NaIO₄ can oxidize Rh 6G, which makes the RTP signal quench. Terbutaline sulfate (TBS) can inhibit NaIO₄ from oxidizing Rh 6G, which makes the RTP signal of Rh 6G enhance sharply. The content of TBS is linear correlation to ΔIp of the system. Based on the facts above, a new inhibition solid substrate-room temperature phosphorimetry (SS-RTP) for the determination of trace TBS has been established. The linear range of this method is 0.0104–2.08 pg spot⁻¹ (corresponding concentration: 0.026–5.2 ng ml⁻¹, with a sample volume of 0.4 μl) with a detection limit (L.D.) of 2.6 fg spot⁻¹ (corresponding concentration: 6.5 × 10⁻¹² g ml⁻¹), and the regression equation of working curve is ΔIp = 2.040 + 54.54 m_TBS (pg spot⁻¹), n = 6, correlation coefficient is 0.9994. For the samples containing 0.0104 pg spot⁻¹ and 2.08 pg spot⁻¹ TBS, the relative standard deviation (RSD) are 3.8% and 2.3% (n = 8), respectively, indicating good precision. This method has been applied to determination of trace TBS in the practical samples with satisfactory results. The reaction mechanism of NaIO₄ oxidizing Rh 6G to inhibit SS-RTP for the determination of trace TBS is also discussed.     

Evaluation of the rate constants of dissociative and ternary recombination reactions of argon ions on the basis of the results of ballistic experiments

AbstractExperimental data on the change in the electron density in the wake of a ballistic object traveling at velocities V _∞=3.4–4.9 km/s in argon at pressures p _∞=30–100 Torr are processed and analyzed. A reaction scheme is proposed which takes into account the recombination of charged particles, processes of ionic conversion, and the excited states of the atom. The solution of the equations of a nonequilibrium boundary layer for flow in the wake is used to formulate the inverse problem of determining the rate constants for dissociative recombination Ar ₂ ⁺ +e→Ar+Ar and ternary recombination Ar⁺+e+Ar→Ar+Ar. The “nearest-neighbor” approximation is used to obtain theoretically an expression for the ternary recombination coefficient as a function of temperature and pressure. Numerous solutions of inverse problems and a comparison with experiments demonstrates the validity of the expression obtained for the ternary recombination coefficient. It is shown that this expression is valid for moderate pressures and complements the Pitaevskii result for low pressures and the Langevin result for high pressures. Zh. Tekh. Fiz. 67, 12–18 (May 1997)     

The pressure broadening and shift for the J=1−0 line of CH3C14N: Resolved and overlapped hyperfine components

Summary Pressure broadening and shift parameters are measured for theJ=1−0 line of CH₃C¹⁴N at 18.4 GHz, both for the three hyperfine components and for the single line which envelopes the hyperfine components, observed at higher pressures (p≥40 mTorr). In agreement with theoretical predictions, these parameters are the same for all the observed lines: Γ _p = (50 ± 5) MHz/Torr,s=(7±2) MHz/Torr. These values are compared with previous measurements, showing a large variance expecially for the shift parameter. The measured broadening parameter is 40% lower than prediction of the Anderson theory.

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Riassunto Sono stati misurati i parametri di allargamento e spostamento per pressione della rigaJ=1−0 del CH₃C¹⁴N a 18.4 GHz. Tali misure sono state eseguite, sulle tre componenti iperfini e sul loro inviluppo osservato a pressionip≥40 mTorr. In accordo con le previsioni teoriche, questi parametri risultano gli stessi per tutte le righe osservate: Γ _p = (50 ± 5) MHz/Torr,s=(7±2) MHz/Torr. Questi valori sono confrontati con quelli delle precedenti misure che mostrano una considerevole dispersione, specialmente per quanto riguarda il parametro di spostamento. L'allargamento per pressione è risultato piú basso di quello previsto dalla teoria di Anderson di circa il 40%.

     

Acidichromism and Ionochromism of Luteolin and Apigenin,the Main Components of the Naturally Occurring Yellow Weld: A Spectrophotometric and Fluorimetric Study

Luteolin and apigenin, extracted from Reseda luteola L., were spectrophotometrically and fluorimetrically studied. The spectra were investigated as a function of pH in methanol/water solutions (1/2, v/v) in the 2–12 pH range. The absorption spectra markedly shifted to the red by increasing the pH. Three acid–base dissociation steps were detected for luteolin (pK _a = 6.9; 8.6; 10.3) and two for apigenin (pK _a = 6.6; 9.3). Fluorescence emission was very weak or undetectable (Φ _F < 10⁻⁴) in acidic solution, but increased in intensity with increasing the pH. Both molecules exhibited a great propensity towards complex formation with metal ions, with association constants on the order of 10⁵–10⁷ for the first complexation step; in the presence of excess Al³⁺ ions, multiple equilibria were detected. A marked fluorescence enhancement was observed upon complexation with Al³⁺ ions (Φ _F ∼ 1 for luteolin and ∼10⁻² for apigenin).     

Xenon induced changes of plasma drop and electron temperature of a thermionic converter

The I–V curves of a thermionic converter were measured for several cesium pressures and various electrode distances, and partial pressures of added xenon as well. The minimum internal voltage drop across the electrode gap was determined and correlated with cesium pressure, spacing and xenon pressure. Without xenon added this voltage drop shows the well-known minimum at an optimum pressure-spacing product ofp _Cs d=5·10⁻²cm·Torr. Only for smaller values of the pressure-spacing product the internal voltage drop can be reduced by the addition of xenon. An interpretation is achieved by a comparatively simple model assuming a uniform electron temperature in the electrode gap. Using this model, the electron temperatures were calculated for various spacings and xenon pressures. Comparing the experimental data of the internal voltage drop and the correspondingly calculated electron temperatures it turns out that, within the framework of the model used, the internal voltage drop is represented by the electron temperature. The electron temperature itself is determined by the ion balance. Presented at the 10th Intersociety Energy Conversion Engineering Conference, Newark, Delaware, USA (1975).     

Bounds on charged lepton mixing with exotic charged leptons

We examine the effects of mixing induced light heavy charged lepton neutral currents on the partial wave amplitude for the process l⁺l⁻ →ZZ (withl = e,μ or τ). By imposing the constraints that the amplitude should not exceed the perturbative unitarity limit at high energy (√s = Λ), we obtain bounds on light heavy charged lepton mixing parameter sin²(2θ _L ^a ) where θ _L ^a is the mixing angle of the ordinary charged lepton with its exotic partner. For Λ = 1 TeV, no bound is obtained on sin² (2θ _L ^a ) form _E < 0.69 TeV. However, sin² (2θ _L ^a ) ≤ 1.52×10⁻⁵ form _E = 5 TeV, sin² (2θ _L ^a ) ≤ 2.41 ×10⁻⁷ form _E = 10 TeV. Similarity for Λ = ∞ no bound is obtained on sin² (2θ _L ^a ) for m_E < 1.97 TeV and sin² (2θ _L ^a ) ≤ 0.15 form _E = 5 TeV and sin² (2θ _L ^a ) ≤ 3.88×10^-2 form _E = 10 TeV.     

Effect of an edge field on the acceptance of a quadrupole mass filter operating at the bottom vertex of the stability rectangle

A quadrupole mass filter (QMF) can operate with a large acceptance and high transmission at the bottom vertex S (a=2.5210, q=2.8153) of the stability quadrilateral. The combined acceptance at a level of 50% transmission and a resolving power of 100 equals 2.0×10⁻³ r ₀ ⁴ f ², which is comparable to the acceptance (5.1×10⁻³ r ₀ ⁴ f ²) of the standard operating regime of a QMF in the first stability region under the same computational conditions and optimal on-axis ion velocity. The acceptance is approximately three times higher in the presence of edge fields than in their absence. The optimal on-axis ion energy equals 1.15r ₀ f, where r ₀ is the radius of the field (the radius of the inscribed circle between the vertices of the electrodes) and f is the working frequency. In the gas-analysis regime a sensitivity of 10⁻⁵ A/Pa is achieved on a mass filter with rod length and rod diameter of 15 cm and 8 mm, respectively, frequency f=1 MHz, and field radius r ₀=0.35 cm. Zh. Tekh. Fiz. 67, 121–124 (October 1997)     

Effect of carbon ion bombardment and surface oxidation on the twinning rate of single-crystal bismuth

A study is made of the change in the dependences of the normal velocity of twinning boundaries on the magnitude of shear stresses in the twinning plane v _n =v _n (τ) in bismuth crystals owing to ion-cluster doping and oxidation of the irradiated surface. Irradiation was by 25 keV carbonions at a dose of 10¹⁷ ion/cm². Twinning of the crystals took place under pulsed loading conditions with pulse durations of 10⁻⁵−10⁻⁴ s and stress amplitudes of (0.2–2.0)×10³ g/mm³. Carbon ion bombardment of single-crystal bismuth causes a shift in the v _n =v _n (τ) curve toward lower stresses. An oxide film slows down the motion of twinning dislocations. Zh. Tekh. Fiz. 69, 130–131 (May 1999)     

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)     

ESR of V4+ in α-RbTiOPO4 single crystals

We have recorded and investigated the ESR spectrum of vanadium-doped α-RbTiOPO₄ single crystals in the temperature interval 77–300 K. Two types of structurally distinct centers, V1 and V2, with a 4:1 ratio of the peak intensities were observed. The angular dependences of the resonance magnetic fields are described by a spin Hamiltonian corresponding to axial symmetry with the parameters g _∥1=1.9305, g _⊥1=1.9565, A _∥1=−168.2×10⁻⁴cm⁻¹, and A _⊥1=−54.3×10⁻⁴cm⁻¹ for V1 centers and g _∥2=1.9340, g _⊥2=1.9523, A _∥2=−169.0×10⁻⁴cm⁻¹, and A _⊥2=−55.2×10⁻⁴cm⁻¹ for V2 centers. A model of a paramagnetic center is proposed: The vanadium ions replace titanium ions in two structurally distinct positions Ti1 and Ti2 (V1 and V2 centers, respectively). The possibility that a VO²⁺ ion forms when α-RbTiOPO₄ crystals and crystals of the KTP group (KTiOPO₄, NaTiOPO₄, α-and β-LiTiOPO₄), studied earlier, are doped with vanadium is discussed. Fiz. Tverd. Tela (St. Petersburg) 40, 534–536 (March 1998)     

Griffith–Kelly–Sherman Correlation Inequalities for Generalized Potts Model

Inspired by the work of D.G.Kelly and S.Sherman on general Griffiths inequalities on correlations in Ising ferromagnets, we formulate and prove Griffith–Kelly–Sherman-type inequalities for the ferromagnetic Potts model with a general number q of local states. We take as local state space for the q-state Potts model the set F ^c  = { − l, − l + 1, ⋯ ,l − 1,l},where l=\fracq-12l=\frac{q-1}{2}. The important properties of F ^c for what follows are that |F ^c | = q and F ^c  = − F ^c .     

Fluorescence spectroscopy of potential electroluminescent materials: Substituent effects on DSB and segmented PPV derivatives

The absorption and fluorescence of substituted distyrylbenzene (DSB) derivatives and segmented poly(phenylene vinylene) (PPV) derivatives are characterized by long-wavelength absorption maxima and absorption coefficients of λ_a = 380–450 nm, ε = 20,000–60,000 M⁻¹ cm¹ and fluorescence maxima, quantum yields, and decay times of λ_r = 440–530 nm, Φ_f = 0.2–0.9, and Τ = 0.8–2.5 ns, respectively. Alkoxy substituents at the central phenylene ring of DSB groups increase the bathochromic shift in the spectra in comparison to DSB, without a significant decrease in the high DSB fluorescence quantum yield. Both phenyl and cyano substitutions at the vinylene bridge lead to a further bathochromic shift of the fluorescence and a decrease in the quantum yield to ca. 0.4. The DSB derivatives and the related segmented PPV derivatives show nearly the same absorption spectra, fluorescence spectra, and radiative rate constantsk _f= Φ_f/Τ, indicating the efficacy of the segmentation of the polymer chain. The radiative rate constants determined by the Φ_f and Τ values and by the Strickler/Berg formula are in reasonable agreement. This supports the possibility of interpreting the properties of the polymers in terms of their DSB units. The decrease in the emission anisotropy can be ascribed to multistep energy transfer processes between different oriented segments.     

Polarization of leading Λ hyperons produced by neutrons on target nuclei

The polarization of the leading Λ hyperons produced on carbon and lead target nuclei by 4–10 GeV neutrons in the angle range Θ<8.5° with respect to the beam and with only neutral-particle accompaniment is measured: 〈Π〉=−0.096±0.018 for C and 〈Π〉=− 0.128±0.047 for Pb. The dependence of the polarization on the transverse momentum and the Feynman variable is measured. The normalized invariant cross section as a function of p _⊥ ² is found to be approximated by the function A exp(−Bp _⊥ ² ), where the parameter B is independent of the kind of nucleus (B=8.71±0.09 (GeV/c)⁻² for carbon and B=8.83±0.18 (GeV/c)⁻² for lead). Pis’ma Zh. éksp. Teor. Fiz. 64, No. 4, 237–240 (25 August 1996)     

Black holes with metric and fields of the same form

We present two rotating black hole solutions with axion ξ, dilaton f{\phi} and two U(1) vector fields. Starting from a non-rotating metric with three arbitrary parameters, which we have found previously, and applying the “Newman–Janis complex coordinate trick” we get a rotating metric g _μν with four arbitrary parameters namely the mass M, the rotation parameter a and the charges electric Q _E and magnetic Q _M . Then we find a solution of the equations of motion having this g _μν as metric. Our solution is asymptotically flat and has angular momentum J = M a, gyromagnetic ratio g = 2, two horizons, the singularities of the solution of Kerr, axion and dilaton singular only when r = a cos θ = 0 etc. By applying to our solution the S-duality transformation we get a new solution, whose axion, dilaton and vector fields have one more parameter. The metrics, the vector fields and the quantity l = x+ie^-2f{\lambda=\xi+ie^{-2\phi}} of our solutions and the solution of: Sen for Q _E , Sen for Q _E and Q _M , Kerr–Newman for Q _E and Q _M , Kerr, Reference Kyriakopoulos [Class. Quantum Grav. 23:7591, 2006, Eqs. (54–57)], Shapere, Trivedi and Wilczek, Gibbons–Maeda–Garfinkle–Horowitz–Strominger, Reissner–Nordstr?m, Schwarzschild are the same function of a, and two functions ρ ² = r(r + b) + a ² cos² θ and Δ = r(r + b) − 2Mr + a ² + c, of a, b and two functions for each vector field, and of a, b and d respectively, where a, b, c and d are constants. From our solutions several known solutions can be obtained for certain values of their parameters. It is shown that our two solutions satisfy the weak the dominant and the strong energy conditions outside and on the outer horizon and that all solutions with a metric of our form, whose parameters satisfy some relations satisfy also these energy conditions outside and on the outer horizon. This happens to all solutions given in the “Appendix”. Mass formulae for our solutions and for all solutions which are mentioned in the paper are given. One mass formula for each solution is of Smarr’s type and another a differential mass formula. Many solutions with metric, vector fields and λ of the same functional form, which include most physically interesting and well known solutions, are listed in an “Appendix”.