Electron-impact excitation cross-sections for the3 S 0−,3 P 0−, and3 D 0-States of a ruthenium atom

The excitation cross-sections of transitions of a ruthenium atom from the³ S ⁰−,³ P ⁰−, and³ D ⁰-levels are measured by the method of extended crossed beams. Based on the results of measurements, the excitation cross-sections of the states are calculated (ignoring cascade contribution). Moscow Power Engineering Institute, 14, Krasnokazarmennaya St., Moscow, E-250, 111250, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 9–13, January–February, 1998.     

One-photon two-electron transitions for metastable helium

We have obtained very accurate excitation energies for helium corresponding to the transitions 2p^{2 3}P^e ↦nln’l’ ³D^o using highly correlated Hylleraas-type wave functions. The doubly excited 2p^{2 3}P^e metastable bound state energy is obtained using Ritz variational principle. The upper bound of 2p^{2 3}P^e energy is –0.7105001556783 a.u., which is close to the best results –0.71050015567833 [R. Hilger et al., Chem. Phys. Lett. 262, 400 (1996)]. We employ complex-coordinate rotation method to obtain ³D^o resonances. The ³D^o resonance energies and widths along with one-photon two-electron transition energies are reported.     

Electron impact excitation cross sections of <Superscript>1</Superscript><Emphasis Type="Italic">F</Emphasis><Superscript>o</Superscript> levels of the strontium atom

The behavior of excitation cross sections of the strontium atom was studied experimentally in the spectral series 5s4d¹D₂-5snf¹F ₃ ^o in the range n = 4–26, and also the optical excitation functions for lines in the same series in the range n = 4–12. It was established that the beginning of the series is perturbed. The effect of the perturbation is manifested both in the irregular course of the dependence of the absolute values of the cross sections on n, and in the difference between the shapes of the optical excitation functions for different terms of the series. The results obtained are compared with available experimental data. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 557–560, September–October, 2007.     

Balmer Hβ vs. Dβ line intensity in the collisions of H+, H2 +, H3 +, D+, D2 +, and D3 + ions with “realistic” metal surface at energies below 1 keV

The intensities of hydrogen H_β and deuterium D_β spectral lines of the Balmer series were measured as a function of collision energy when H⁺, H₂ ⁺, H₃ ⁺, D⁺, D₂ ⁺, and D₃ ⁺ ions impinged on Al, Ti, Cu, Mo, W, and Pb targets. The collision energies were kept in the 100–1000 eV range. The target surface was contaminated with hydrocarbons from the vacuum pumping system and possibly also by oxygen molecules due to limited vacuum conditions. At projectile velocities above 200 km/s the luminescence of backscattered deuterium atoms is about 30–50% weaker than that of hydrogen atoms.     

Variation of interface trap level charge density within the bandgap of 4H-SiC with varying oxide thickness

Interfacial characteristics of metal oxide-silicon carbide (MOSiC) structure with different thickness of SiO₂, thermally grown in steam ambient on Si-face of 4H-SiC (0 0 0 1) substrate were investigated. Variations in interface trapped level density (D _it) was systematically studied employing high-low (H-L) frequency C–V method. It was found that the distribution of D _it within the bandgap of 4H-SiC varied with oxide thickness. The calculated D _it value near the midgap of 4H-SiC remained almost stable for all oxide thicknesses in the range of 10⁹–10¹⁰ cm⁻² eV⁻¹. The D _it near the conduction band edge had been found to be of the order of 10¹¹ cm⁻² eV⁻¹ for thicker oxides and for thinner oxides D _it was found to be the range of 10¹⁰ cm⁻² eV⁻¹. The process had direct relevance in the fabrication of MOS-based device structures.     

Kinetics of the photoconductivity and absorption in the D −(A +) bands in doped silicon

The photoconductivity (PC) spectra and the induced absorption of background radiation in the energy range 10–40 meV are investigated in weakly compensated B-, Ga-, and As-doped silicon at 4.2 K. It is shown that dips corresponding to the photoionization of long-lived excited states of B and As are observed in the PC spectra on the D ⁻(A ⁺) bands. It is found that the frequency dependence of the PC spectra corresponds to excitation relaxation times of the order of 10⁻⁴ s for the states in the D ⁻ (A ⁺) bands. It is established that in electric fields E>100 V/cm the PC decreases sharply, while the induced absorption of the background radiation changes very little. This confirms the conclusion that the excitation of the D ⁻ (A ⁺) itself makes the main contribution to the PC. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 4, 224–227 (25 August 1997)     

Erbium electroluminescence excitation in amorphous hydrogenated silicon under thermally stimulated deep-center tunneling ionization

A study of the electroluminescence of erbium-doped, amorphous hydrogenated silicon, a-Si:H 〈Er〉, is reported. It has been found that the electroluminescence intensity at the wavelength λ=1.54 μm corresponding to the ⁴ I _13/2→⁴ I _15/2 intra-4f shell transition in Er passes through a maximum near room temperature. The unusual temperature and field dependences of the electroluminescence indicate electric-field induced multi-phonon tunneling emission of electrons from deep centers. The electroluminescence of Er³⁺ ions is due to their becoming excited as conduction-band electrons are captured by neutral dangling bonds (D ⁰ centers), which form when erbium is incorporated into the amorphous matrix. This Auger process transforms the center from its neutral state, D ⁰, to a negatively charged state, D ⁻, and the energy released in the capture is transferred by Coulomb interaction into the erbium-ion 4f shell. The steady-state current through the electroluminescent structure is supported by the reverse process of multi-phonon tunneling-electron emission from the D ⁻ center to the conduction band. The proposed theoretical model is in a good agreement with experimental data. Fiz. Tverd. Tela (St. Petersburg) 41, 210–217 (February 1999)     

Absorption spectrum of HDO in the 1.06 μm region at a temperature of 1000 K

In the 9387–9450 cm^–1 region at temperatures of 300–1000 K, we have used an intracavity laser spectrometer based on a neodymium laser with threshold sensitivity to absorption 10^–8 cm^–1 and spectral resolution 0.035 cm^–1 to study the absorption spectrum of D₂¹⁶O, H₂¹⁶O, and HD¹⁶O vapor. The high-temperature spectrum contains more than 450 absorption lines, 240 of which are assigned to the HDO isotopomer. The absorption lines of HDO were identified and belong to nine vibrational transitions: 3ν₂ +ν₃, 2ν₁ + 3ν₂, 2ν₁ + ν₃, 4ν₂ + ν₃, 7ν₂, ν₁ + 2ν₂ + ν₃, ν₁ + 5ν₂, ν₁ + 2ν₂, and 3ν₃ – ν₂.     

Baryon decay of excited states of 1P-shell hypernuclei

The baryon decays of hypernuclear resonances with the configurations s_⃛p⁻¹, p_⃛p⁻¹, and s_⃛s⁻¹ are analyzed within the framework of a translationally invariant shell model. Particular attention is paid to the influence of the nuclear structure on the decay probabilities in different channels. Joint Institute of Nuclear Research, Dubna. Institute of Nuclear Physics, Czech, Republic, Rzhezh. Institute of Nuclear Research, Russian Academy of Sciences, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 35–51, October, 1997.     

Determination of parameters of Cu surface mass transport on sapphire from morphological changes of beaded films caused by evaporation

s , the surface diffusion coefficient, D_s ^′, and the surface reaction rate coefficient, β_s ^′, of Cu on alumina are determined in the temperature range 1048–1198 K. Measuring simultaneously the time dependence of the effective thickness, H_eff(t), the lateral shift of the boundary, y(t) of beaded films (BF) and using vapour pressure data we concluded that the process is controlled by surface reaction at the perimeters of beads. Supposing Arrhenius-type temperature dependence for D_s ^′, β_s ^′ and λ_s the activation energies and preexponential factors have been calculated. Received: 2 October 1996/Accepted: 27 November 1996     

Experimental investigation of variability of ultraviolet fluxes at the earth's surface

Some results of two years of regular measurements of UV radiation at the earth's surface in Siberia (56.5^o N, 85^o E) are given. It is shown that the presence of snow cover increases the UV irradiation of the earth by scattered radiation by 9–15%. In cloudless but windy weather, quasi-periodic fluctuations of UV irradiation with periods of 5–15 min and with fluctuation swings of 1–10% are observed. Low-level, heavy cloudiness in summer considerably reduces (by an average of 30–35%) UV irradiation, especially when the sun is low (down to 30^o). Mid-and upper-level clouds increase the UV irradiation of the earth by scattered radiation. When the sun is high (30–50^o) and there is heavy cloudiness, this increase can reach 28% in the UV-A spectral range. Tomsk State University. Academician V. D. Kuznetsov Siberian Physics and Technology Institute, Tomsk State University. Institute of Optical Monitoring, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 71–74, September, 1998.     

Facile patterning of luminescent GdVO4:Ln (Ln?=?Eu3+, Dy3+, Sm3+) thin films by microcontact printing process

Ordered arrays of luminescent GdVO₄:Ln (Ln = Eu³⁺, Dy³⁺, Sm³⁺) films with dot patterns have been successfully fabricated via microcontact printing method. The soft-lithography process utilizes a PDMS elastomeric mold as the stamp combined with a Pechini-type sol–gel process to produce luminescent patterns on quartz plates, in which a GdVO₄:Ln (Ln = Eu³⁺, Dy³⁺, Sm³⁺) precursor solution was employed as ink. The ordered luminescent GdVO₄:Ln patterns were revealed by optical microscopy and their microstructure, consisting of nanometer-scale particles, as demonstrated by scanning electronic microscopy observations. In addition, photoluminescence and cathodoluminescence were carried out to characterize the patterned GdVO₄:Ln (Ln = Eu³⁺, Dy³⁺, Sm³⁺) samples. Upon UV-light or electron-beam irradiation, the rare earth ions Eu³⁺, Dy³⁺, and Sm³⁺ in the crystalline GdVO₄ host show their characteristic transitions dominated by ⁵D₀–⁷F₂, ⁴F_9/2–⁶H_13/2 ,and ⁴G_5/2–⁶H_7/2, respectively. These results make the combining soft lithography with a Pechini-type sol–gel route have potential applications as rare-earth luminescent pixels for next-generation field-emission display devices.     

Remote detection of sulfur dioxide by means of a CO2 laser

The possibility of remote detection of SO₂ in the 9-μm region of the spectrum by means of a TEA CO₂ laser was theoretically and experimentally investigated with regard to the real state of the atmosphere and the contribution of background concentrations of H₂O, CO₂ and NH₃ to absorption. For sounding along short paths (2L=2 km), the method of detection of small concentrations of SO₂ (at the MPC level) with the use of the lines of the CO₂-molecule regular transitions (00^o1–02^o0 band) has been devised and experimentally tested. It is shown that in sounding along longer paths (2L=6 km), a noticeable increase in sensitivity can be achieved by the generation lines of the CO₂-molecule sequential 00^o2–02^o1 band. B. I. Stepanov Institute of Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 508–515, July–August, 1998.     

Production of excited charm and charm-strange mesons at HERA

The production of excited charm, D ₁(2420)⁰ and D ₂^*(2460)⁰, and charm-strange, D _s1(2536)^±, mesons in ep collisions was measured with the ZEUS detector at HERA using an integrated luminosity of 126 pb⁻¹. Masses, widths and helicity parameters were determined. The measured yields were converted to the rates of c quarks hadronising as a given excited charm meson and to the ratios of the dominant D ₂^*(2460)⁰ and D _s1(2536)^± branching fractions. A search for the radially excited charm meson, D ^*′(2640)^±, was also performed. The results are compared with those measured previously and with theoretical expectations. Dedicated to the memory of our colleague Pavel Ermolov. Deceased. Also affiliated with University College London, UK. Now at BayesForecast, Madrid, Spain. Also at Institut of Theoretical and Experimental Physics, Moscow, Russia. Also at INP, Cracow, Poland. Also at FPACS, AGH-UST, Cracow, Poland. Partly supported by Moscow State University, Russia. Royal Society of Edinburgh, Scottish Executive Support Research Fellow. Also affiliated with DESY, Germany. Also at University of Tokyo, Japan. Now at Kobe University, Japan. Supported by DESY, Germany. Now at University of Salerno, Italy. Partly supported by Russian Foundation for Basic Research grant no. 05-02-39028-NSFC-a. Partially supported by Warsaw University, Poland. This material was based on work supported by the National Science Foundation, while working at the Foundation. Now at University of Kansas, Lawrence, USA. Also at Max Planck Institute, Munich, Germany, Alexander von Humboldt Research Award. Now at KEK, Tsukuba, Japan. Now at Nagoya University, Japan. Member of Department of Radiological Science, Tokyo Metropolitan University, Japan. Now at SunMelx Co. Ltd., Tokyo, Japan. PPARC Advanced fellow. Supported by the research grant no. 1 P03B 04529 (2005–2008). Also at Hamburg University, Inst. of Exp. Physics, Alexander von Humboldt Research Award and partially supported by DESY, Hamburg, Germany. Also at Łódź University, Poland. Member of Łódź University, Poland. Now at Lund Universtiy, Lund, Sweden. This work was supported in part by the Marie Curie Actions Transfer of Knowledge project COCOS (contract MTKD-CT-2004-517186). Now at University of Bonn, Germany. Now at DESY group FEB, Hamburg, Germany. Now at University of Liverpool, UK. Now at CERN, Geneva, Switzerland. Now at Bologna University, Bologna, Italy.     

Wavelengths for 2pnp 1Pe→2pnd 1Do and 2pnp 3Pe→2pnd 3Do transitions in Li II,Be III,B IV,C V using correlated exponential wave functions

Doubly-excited ^1,3P^e and ^1,3D^o states of Li II, Be III, B IV, C V are calculated using highly correlated exponential wave functions within the framework of Ritz variational principle. The wavelengths for the 2pnp ¹P^e→2pn′d ¹D^o (n, n′≤7) and 2pnp ³P^e→2pn′d ³D^o (n, n′≤7) transitions are reported. Our present results for the 2pnp ^1,3P^e and 2pnd ^1,3D^o states energies are accurate in precision compared to the results of previous calculations. Comparisons are also made with the experimental results. The effective quantum numbers (n^?) for the 2pnp ^1,3P^e and 2pnd ^1,3D^o states are also reported.     

Nature of conduction via impurities in uncompensated silicon

The static conductivity σ(E) and photoconductivity (PC) at radiation frequencies ħω=10 and 15 meV in Si doped with shallow impurities (density N=10¹⁶−6×10¹⁶ cm⁻³, ionization energy ε₁≃45 meV) with compensation K=10⁻⁴−10⁻⁵ in electric fields E=10–250 V/cm are measured at liquid-helium temperatures T. Special measures are taken to prevent the high-frequency part of the background radiation (ħω>16 meV) from striking the sample. It is found that the conductivity σ(E) is due to carrier motion along the D ⁻ band, which is filled with carriers under the influence of the field E. In fields E<E _q (E _q ≃100–200 V/cm) the carrier motion consists of hops along localized D ⁻ states in a 10–15 meV energy band below the bottom of the free band (energy ε=ε₁); for E>E _q carriers drift along localized D ⁻ states with energy ε∞ε₁−10 meV. An explanation is proposed for the threshold behavior of the field dependence of the photo-and static conductivities. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 4, 232–236 (25 August 1997)     

Interactions of charmed mesons with nucleons in the ¯<Emphasis Type="Italic">p</Emphasis><Emphasis Type="Italic">d</Emphasis> reaction

We study the possibility to measure the elastic ΦN (Φ≡J/ψ,ψ(2S), ψ(3770), χ_2c) scattering cross section in the reaction ˉp+d→Φ+n _sp and the elastic D(ˉD)N scattering cross section in the reaction ˉp+d→D ⁻ D ⁰ p _sp. Our studies indicate that the elastic scattering cross sections can be determined for Φ momenta about 4–6 GeV/c and D/ˉD momenta 2–5 GeV/c by selecting events with p _t≥ 0.4 GeV/c for Φ's and p _t(p _sp) ≥ 0.5 GeV/c for D/ˉD-meson production. Received: 8 November 1999     

Radiative lifetime and oscillator strength determination in Mg-like potassium (K VIII)

Theoretical transition probabilities have been obtained for 54 n = 3 transitions depopulating the 3s3p ¹P^o, 3p^{2 3}P, ¹D, ¹S, 3s3d ¹D, ³D and 3p3d ³P^o, ³D^o, ³F^o, ¹F^o, ¹D^o, ¹P^o levels, including 14 transitions not yet observed. Some of these predictions have been compared with experimental lifetimes obtained by beam-foil spectroscopy for four n = 3 levels of K⁷⁺. An excellent agreement is observed between theory and experiment for all the levels. Received 23 January 2002 / Received in final form 23 April 2002 Published online 19 July 2002     

Photoconductivity of Cu x Ag1−x Cd2InTe4

Summary The prominent photoelectric parameters of the semiconducting solid solutions Cu _x Ag_1−x Cd₂InTe₄ are reported. From the spectral dependence of photoconductivity at room temperature and at 77 K the energy gaps and their thermal coefficients are obtained. The detectivityD ^*, the photocurrent gainG and the carrier lifetime are measured and the carrier mobility is deduced. In order to improve theD ^* characteristics, the analysis of its parameters is also performed. Paper presented at the ?V International Conference on Ternary and Multinary Compounds?, held in Cagliari, September 14–16, 1982.