Showing papers in "Physica Scripta in 1997"
TL;DR: In this paper, an interpretation of the f-oscillator is provided as corresponding to a special nonlinearity of vibration for which the frequency of oscillation depends on the energy.
Abstract: The notion of f-oscillators generalizing q-oscillators is introduced. For classical and quantum cases, an interpretation of the f-oscillator is provided as corresponding to a special nonlinearity of vibration for which the frequency of oscillation depends on the energy. The f-coherent states (nonlinear coherent states) generalizing q-coherent states are constructed. Applied to quantum optics, photon distribution function, photon number means, and dispersions are calculated for the f-coherent states as well as the Wigner function and Q-function. As an example, it is shown how this nonlinearity may affect the Planck distribution formula.
571 citations
TL;DR: The authors discussed with George Series the experiments in my group to measure the electric dipole moments of the proton and electron using the magnetic resonance in molecules and found that the current interest in this kind of measurement and he wanted to find out why we use molecules rather than something simple like the hydrogen atom.
Abstract: Some years ago while on sabbatical leave in Oxford I discussed with George Series the experiments in my group to measure the electric dipole moments of the proton and electron using the magnetic resonance in molecules. He asked about the current interest in this kind of measurement and he wanted to find out why we use molecules rather than something simple like the hydrogen atom. After about an hour, George was satisfied with the answers I gave him, but on several occasions after that, he encouraged me to write up some notes about all this. Well George, here they are.
92 citations
TL;DR: The Electron Beam Ion Trap (EBIT) facility at the National Institute of Standards and Technology (NIST) is now operational and producing atomic physics data as mentioned in this paper, and a preview of some of the first atomic physics results is given to illustrate the capabilities of the facility.
Abstract: The Electron Beam Ion Trap (EBIT) facility at the National Institute of Standards and Technology (NIST) is now operational and producing atomic physics data. This report gives an overview of the design, operation, and performance of our EBIT. A preview of some of the first atomic physics results is given to illustrate the capabilities of the facility.
62 citations
TL;DR: A new Electron Beam Ion Trap has recently been completed in Tokyo as mentioned in this paper, and the general features of the apparatus, design and operation are given, as well as the planned and ongoing experimental program.
Abstract: A new Electron Beam Ion Trap has recently been completed in Tokyo. The general features of the apparatus, design and operation are given. This paper also surveys the planned and ongoing experimental program.
56 citations
TL;DR: In this article, an optical gas concentration measurement system based on an electrically tuneable micromachined Fabry-Perot interferometer (FPI) is described.
Abstract: This paper describes an optical gas concentration measurement system, which is based on an electrically tuneable micromachined Fabry-Perot interferometer (FPI). The operating principle of the system is NDIR Single-Beam Dual-Wavelength measurement. The FPI is tuned so that the pass band coincides with the absorption band of the measured gas; a detector records the strength of the signal getting through the measurement chamber. The pass band of the FPI is then shifted to either side of the absorption band; the detected signal constitutes the reference signal. The ratio of these two signals indicates the degree of light absorption and so the gas concentration. Properties of the FPI are discussed, as well as the performance of the measurement system.
54 citations
TL;DR: In this article, the spectrum of iodine was photographed on a 3m normal incidence spectrograph at the Antigonish laboratory using a triggered spark source in the 300-1200 A region.
Abstract: The spectrum of iodine was photographed on a 3-m normal incidence spectrograph at the Antigonish laboratory using a triggered spark source in the 300-1200 A region. Eleven out of twelve levels of the 5p5d configuration and all four levels of the 5p6s configuration of I VI have been established. The missing level 5p2 1S0 has been located and two levels 5s5d 1D2 and 5s6s 1S0 reported earlier have been revised. The beam foil spectra obtained at the University of Alberta in Edmonton complemented the spark data. The least-square-fitting (LSF) and Hartree-Fock calculations were carried out to interpret the level scheme. Sixty-six new lines have been classified in this spectrum.
49 citations
TL;DR: In this paper, the Lund Fourier transform (LFT) was used to obtain 75 new energy levels of Au II, and improved values were given for the previously known levels of the 5D10, 5D96s, 5d96s 2, 5 D96d 6p and 5D97p configurations.
Abstract: Spectra of gold, emitted from a hollow-cathode discharge, have been recorded with the Lund Fourier transform spectrometer in the region 1800-8000 A. Complementary photographic spectrograms in the region 800-1900 A have been obtained using the 10.7 m normal incidence spectrograph at Observatoire de Paris, Meudon. The term analysis has yielded 75 new energy levels of Au II, and improved values are given for the previously known levels of the 5d10, 5d96s, 5d86s2, 5d97s, 5d96d, 5d96p, 5d86s6p and 5d97p configurations. The new levels belong to the 5d86s2, 5d96d, 5d98s, 5d86s6p, 5d97p and 5d76s26p configurations. About 450 identified Au II lines with a wavelength uncertainty of about 1 mA are reported. The energy level structure has been studied by using the Slater-Condon parametric method. The ionization limit has been determined to 162950 ± 200 cm−1.
47 citations
TL;DR: In this paper, the formation of one-dimensional spatial structures in degenerate optical parametric oscillation due to diffraction effects is discussed and their analogy with parametrically excited localized structures studied in hydrodynamics is illustrated.
Abstract: Formation of one-dimensional spatial structures in degenerate optical parametric oscillation due to diffraction effects is discussed and their analogy with parametrically excited localized structures studied in hydrodynamics is illustrated. It is shown that, when the emergence of roll paterns is inhibited by cavity constraints, localized structures in the form of bright or dark solitary waves for the signal field may be generated for appropriate detunings of the pump field from a cavity resonance. The dark waves exist when bifurcation is supercritical and are stable close to threshold, whereas bright waves spontaneously arise in the subcritical case for large pump detunings and below threshold for oscillation due to a modulational instability of the homogeneous state.
46 citations
TL;DR: A new Electron-Beam-Ion-Trap (EBIT) has been installed at the Max Planck Institute of Plasmaphysics Berlin branch as discussed by the authors, which consists in producing and trapping highly charged ions inside the charge of an electron beam and measuring the emitted x-ray radiation.
Abstract: A new Electron-Beam-Ion-Trap (EBIT) has been installed at the Max Planck Institute of Plasmaphysics Berlin branch. The experimental technique consists in producing and trapping highly charged ions inside the space charge of an electron beam and measuring the emitted x-ray radiation. During the first test phase x-ray spectra of highly charged Ba, W and Ar-ions were observed.
44 citations
TL;DR: In this article, the total cross sections for the near threshold η production in proton-proton collisions have been investigated with the assumption that the production mechanism is due to the emission of a meson x(π,η,σ) from one of the nucleons followed by a xN → ηN transition on the second nucleon.
Abstract: The total cross sections for the near threshold η production in proton-proton collisions has been investigated with the assumption that the production mechanism is due to the emission of a meson x(π,η,σ) from one of the nucleons followed by a xN → ηN transition on the second nucleon. The xN → ηN amplitudes are generated from the unitary multi-channel multi-resonance model which has recently been constructed by fitting the data of πN elastic scattering and πN → ηN reaction. The initial and final pp distortions are calculated from a coupled-channel πNN model which describes the NN scattering data up to about 2 GeV. With the xNN vertex functions taken from the Bonn potential, the predicted total cross sections of threshold pp → ηpp reaction are in good agreement with the data. In contrast to previous works, we find that the η-exchange plays an important role.
43 citations
TL;DR: In this paper, the authors showed that the Coulomb explosion model can not explain the sputtering of SiO2 and that the potential sputtering can be explained as a defect mediated sputtering process which is well known in electron stimulated desorption.
Abstract: The total sputter yield for Au, Si, GaAs, SiO2, MgO, LiF and NaCl bombarded with hyperthermal highly charged Arq+ ions (q = 1-9) has been measured. Only for alkali halides (LiF, NaCl) and to some extent for SiO2 potential sputtering (enhancement of the sputter yield with increasing charge state of the primary ion) has been observed. All other targets showed normal collision induced sputtering. From that result it is obvious that the mechanisms for sputtering can not be explained by the Coulomb explosion model, because in this model insulators like MgO and semiconductors like Si and GaAs should also show charge state dependence of the sputtering yield. Alkali halides and SiO2 are materials which are known for strong electron phonon coupling where electronic excitations in the valence band are localized by formation of self trapped excitons (STE) and/or self trapped holes (STH). During bombardment with highly charged ions the neutralization process in front of, at and below the surface causes the formation of STE and/or STH. Therefore the potential sputtering can be explained as a defect mediated sputtering process which is well known in electron stimulated desorption (ESD) where the decay of STH and/or STE into different colour centers leads at the end to the desorption of neutralized anions. The also created neutral cations are either evaporated (as it is the case for the alkali halides) or have to be removed by momentum transfer by the impinging projectiles. Therefore it is very likely that in the case of SiO2 for very low impact energy mainly only oxygen is enhanced sputtered, the surface is enriched in Si and the potential sputtering effect decreases with increasing ion dose.
TL;DR: Using a photon-ion merged-beam technique, this paper studied the photoionization of multiply charged Xeq+ (q = 1-3) ions in the 4d excitation region (50-140 eV).
Abstract: Using a photon-ion merged-beam technique, we studied the photoionization of multiply charged Xeq+ (q = 1-3) ions in the 4d excitation region (50-140 eV). Relative yield spectra of photoions created by single (q → q + 1) and double (q → q + 2) photoionization were measured as a function of photon energy. A broad "4d giant resonance" peak with some preceding discrete peaks appears in each total ion spectrum. The intensities of discrete peaks observed at around 4d ionization threshold strongly depend on the target charge state. Those for Xe3+ target are very strong, whereas those for Xe+ are weak. Peaks due to 4d → 5p transition, which cannot occur in the neutral Xe case, has also been observed for each ion-target. The experimental spectrum for Xe+ has been analyzed by a multiconfiguration Dirac-Fock calculation. This calculation shows that results observed may be explained in terms of the correlation of valence and excited orbitals, and the effect of 4f-orbital collapse, of which the degree varies strongly with the change of the effective nuclear charge.
TL;DR: Perturbation theory for elliptic pulsons is developed and predicts pulson and eccentricity oscillations as mentioned in this paper, and the pulson oscillation period is predicted qualitatively correct.
Abstract: Perturbation theory for elliptic pulsons is developed and predicts pulson and eccentricity oscillations. The pulson oscillation period is predicted qualitatively correct.
TL;DR: In this paper, the absolute yield of L-subshell x-rays emitted from a target of a given element and thickness when it was bombarded with a known flux of photons of given energy was measured using two excitation sources.
Abstract: L1, Lα, Lβ and Lγ XRF cross-sections were measured in heavy elements 73 ≤ Z ≤ 92 at excitation energies of 59.5 and 123.6 keV photons. Measurements were made using two excitation sources. The experimental values of the cross-sections were determined by measuring the absolute yield of L-subshell x-rays emitted from a target of a given element and thickness when it was bombarded with a known flux of photons of given energy. It is observed that the measured L XRF cross-section values for the elements are in general agreement with the theoretical ones evaluated using L-subshell fluorescent yields (ωi) and Coster-Kronig transition probabilities (fij) based on the relativistic Dirac-Hartree-Slater theory. The present and previous measured and calculated values of the cross-sections are tabulated to bring out the existing status of L x-rays production cross-sections.
TL;DR: In this article, a linear dispersion relation for electrostatic dust-acoustic waves has been derived, taking into account the dynamics of neutral atoms in weakly ionized dusty plasmas.
Abstract: A linear dispersion relation for electrostatic dust-acoustic waves has been derived, taking into account the dynamics of neutral atoms in weakly ionized dusty plasmas. Explicit expressions for the temporal and spatial attenuation rates of dust-acoustic waves due to collisions of ions and dust grains with neutral atoms are presented.
TL;DR: Using the Oxford electron beam ion trap (EBIT), this article studied a number of magnetic-dipole fine-structure transitions in highly charged argon and barium, which lie in the visible and near-UV region of the spectrum.
Abstract: Using the Oxford electron beam ion trap (EBIT), we have studied a number of magnetic-dipole fine-structure transitions in highly charged argon and barium, which lie in the visible and near-UV region of the spectrum Our wavelength measurements, with uncertainties of between 7 and 20 ppm, are the most accurate yet reported using an EBIT as a spectroscopic source of ions, and provide a useful test of atomic structure calculations for many-electron systems The argon transitions studied are also of astrophysical interest Finally, we present the first studies of the polarization of a visible transition from a highly charged ion trapped in an EBIT
TL;DR: In this article, changes of the moments of atomic spectrum due to configuration interaction (CI), the CI strength, the average shift of the energy of a level due to its interaction with all levels of distant configuration and other global characteritics of CI effects in atoms are systematised and their expressions presented.
Abstract: Changes of the moments of atomic spectrum due to configuration interaction (CI), the CI strength, the average shift of the energy of a level due to its interaction with all levels of distant configuration and other global characteritics of CI effects in atoms are systematised and their expressions presented. The results of the calculation of these characteristics for the energy level spectra of the 3s3p3 + 3s23p3d configurations in Si isoelectronic series, 3p53dN + 3p63dN−24p + 3p63dN−24f (N = 5, 6, 7, 8) in Cr, Mn, Fe and Co isoelectronic series, ns2 npN + npN+2 at n = 2 – 5 and N = 2 – 4 in neutral atoms as well as for the characteristic emission spectra corresponding to the 3p53d9 + 3d74p → 3d8 transitions as well as for the Auger M4,5N1N2,3 spectra in Kr and N4,5O1O2,3 in Xe are given and compared with the same characteristics of the more complete experimental spectra.
TL;DR: In this paper, the transition probabilities for 30 lines of Pb II were determined by measuring the intensities of the emission lines of a laser-produced plasma (LPP) in an atmosphere of Ar. The experimental results obtained during this study have been compared with the experimental and theoretical values given by other authors.
Abstract: Transition probabilities have been determined for 30 lines of Pb II by measuring the intensities of the emission lines of a laser-produced plasma (LPP) of Pb in an atmosphere of Ar. The plasma has been seen to contain local thermodynamic equilibrium (LTE) and homogeneity; the plasma studied has a temperature of 11 500 K and an electron density of 1016 cm−3. The experimental results obtained during this study have been compared with the experimental and theoretical values given by other authors.
TL;DR: In this article, a model is introduced to describe negative first return strokes in lightning ground flashes, and the basic assumptions made are similar to those used previously to describe the subsequent return strokes.
Abstract: A model is introduced to describe negative first return strokes in lightning ground flashes. The basic assumptions made are similar to those used previously to describe the subsequent return strokes. The model predictions are in general agreement with experimental observation. The model predicts the relationships between (a) peak current and the peak electric radiation field and (b) the peak derivatives of current and electric radiation field. These relationships can be used in the remote sensing of first return stroke current parameters through the measured radiation fields.
TL;DR: In this article, a general algebraic method for investigating the diagonalizability of a composite system observable in the non-correlated basis of the Hilbert state space of a two-body quantum system was developed.
Abstract: We develop a general algebraic method for investigating the diagonalizability of a composite-system observable in the, so-called, noncorrelated basis of the Hilbert state space of a composite (two-body) quantum system. The method consists in rewriting a composite-system obsrvable in linear form, for which one directly and uniquely obtains an answer concerning the diagonalizability. The method has been applied to the analysis of the concept of separability of the interaction part of the Hamiltonian of the composite system, quantum system plus environment (apparatus). The application leads to a new (more precise) operational definition of separability, which represents a necessary condition concerning the occurrence of decoherence in the, so-called, orthodox approach to the theory of decoherence.
TL;DR: In this paper, high resolution spectra of neutral vanadium excited in a hollow cathode discharge with helium, neon and argon as carrier gases were recorded in the infrared region (1800-9000 cm−1) by Fourier transform spectroscopy.
Abstract: High resolution spectra of neutral vanadium excited in a hollow cathode discharge with helium, neon and argon as carrier gases have been recorded in the infrared region (1800-9000 cm−1) by Fourier transform spectroscopy. A detailed analysis of the spectra has allowed to determine some missing terms in the doublet, quartet and sextet systems of the configurations 3d5, 3d34s5p, 3d44s, 3d44s, and 3d45d of V I. Investigation of the hyperfine structure patterns has confirmed the identification of the transitions and has given rise to the determination of 67 new magnetic dipole constants.
TL;DR: In this article, the authors explore the effects of the proximity to a superconductor on the level density of a billiard for the two extreme cases that the classical motion in the billiard is chaotic or integrable.
Abstract: We explore the effects of the proximity to a superconductor on the level density of a billiard for the two extreme cases that the classical motion in the billiard is chaotic or integrable. In zero magnetic field and for a uniform phase in the superconductor, a chaotic billiard has an excitation gap equal to the Thouless energy. In contrast, an integrable (rectangular or circular) billiard has a reduced density of states near the Fermi level, but no gap. We present numerical calculations for both cases in support of our analytical results. For the chaotic case, we calculate how the gap closes as a function of magnetic field or phase difference.
TL;DR: In this paper, a casting of polyvinylchloride (PVC) films containing different amounts of NiCl2 was performed using a casting method and the spectral analysis indicated that the Ni+2 ions are present in its octahedral symmetrical forms.
Abstract: Polyvinylchloride (PVC) films containing different amounts of NiCl2 have been prepared using a casting method. The UV/VIS (200-800 nm) and IR (200-4000 cm−1) spectra and dc electric conductivity have been investigated. One optical absorption edge was found for pure PVC, while the addition of NiCl2 led to the appearance of a second edge at lower photon energy. The change of the calculated values of the optical energy gaps with increasing NiCl2 content has been interpreted in terms of the structural modifications of the PVC matrix. The spectral analysis indicated that the Ni+2 ions are present in its octahedral symmetrical forms. The infrared analysis revealed that there is a change of the NiCl2 chliation mode beyond 0.25 filling level. The electric conduction was attributed to an intrachain one dimensional interpolaron hopping mechanism. The calculated hopping distance was R0 ≥ five monomer unit lengths. R0 depends linearly on both temperature and filling level.
TL;DR: In this paper, the electric dipole transitions in the nitrogen isoelectronic sequence (Z = 10-30) between the levels of the 1s22s22p3, 1s 22s2p4 and 1 s22p5 configurations are considered.
Abstract: The electric dipole transitions in the nitrogen isoelectronic sequence (Z = 10-30) between the levels of the 1s22s22p3, 1s22s2p4 and 1s22p5 configurations are considered. The stationary second-order many-body perturbation theory (MBPT) is used to account for the electron correlations. Non-local potential is used to calculate the radial part of the effective Hamiltonian. Relativistic corrections were included in the Breit-Pauli approximation. The results include energies, wavelengths, and oscillator strengths for all N-like ions in the interval Z = 10-30.
TL;DR: In this article, a theoretical analysis of the relative intensities of the Doppler-free signals in saturation spectroscopy, velocity selective optical pumping (VSOP) spectrographs, polarization spectrograms, and a mixing of saturation and polarization spectroscopies is presented using the approximation of a single cycle of optical pumping.
Abstract: A theoretical analysis of the relative intensities of the Doppler-free signals in saturation spectroscopy, velocity selective optical pumping (VSOP) spectroscopy, polarization spectroscopy and a mixing of saturation and polarization spectroscopies is presented using the approximation of a single cycle of optical pumping in a four-level system. An optical pumping process in the Zeeman sublevels is taken into account owing to the important role of spontaneous emission even if the sublevels are degenerate. Arbitrary polarization combinations are considered for pump and probe beams. The similarities and differences between three kinds of spectroscopy are made clear. Both circular and linear optical anisotropies induced by the pump beam are considered in this theoretical calculation. The magnitude and sign of Doppler-free resonances in each spectroscopy are quite different owing to the polarizations of the pump and probe beams. The four-level system is important as a three-level approximation. The results obtained from the four-level optical pumping theory are in good agreement with experimental reports.
TL;DR: In this paper, the authors consider two special types of the parameter-free Ginzburg-Landau equation, viz., the ones that combine the bandwidth-limited linear gain and nonlinear dispersion, or the broadband gain, linear dispersion and non linear losses.
Abstract: We consider in detail two special types of the parameter-free Ginzburg-Landau equation, viz., the ones that combine the bandwidth-limited linear gain and nonlinear dispersion, or the broadband gain, linear dispersion, and nonlinear losses. The models have applications in nonlinear fiber optics and traveling-wave convection. They have exact solitary-pulse solutions which are subject to a background instability. In the former model, we find that the solitary pulse is much more stable than a "densely packed" multi-pulse array. On the contrary to this, a multi-pulse array in the latter model is destroyed by the instability very slowly. Considering bound states of two pulses, we conclude that they may form a robust bound state in both models. Conditions which allow for formation of the bound states qualitatively differ in the two models.
TL;DR: In this paper, the normalization relation between the bound and scattering S-state wave functions, extrapolated to the bound state pole, is derived from the Schrodinger equation, and the result does not depend on the details of the potential through the corresponding Jost function but is given uniquely in terms of the binding energy.
Abstract: The normalization relation between the bound and scattering S-state wave functions, extrapolated to the bound state pole, is derived from the Schrodinger equation. It is shown that, unlike previous work, the result does not depend on the details of the potential through the corresponding Jost function but is given uniquely in terms of the binding energy. The generalization to higher partial waves is also given.
TL;DR: In this paper, a modified Kadomtsev-Petviashvili (MKP) equation is proposed, which is a weakly two-dimensional generalisation of the Schamel equation.
Abstract: A modified Kadomtsev–Petviashvili (MKP) equation is proposed. The equation is a weakly two-dimensional generalisation of the Schamel equation. It is shown that one form of this equation arises in the context of the propagation of ion-acoustic waves in a plasma with non-isothermal electrons. The stability of certain plane periodic and solitary travelling wave solutions of the MKP equation to two-dimensional long wavelength perturbations is investigated using the method of Rowlands and Infeld. The results obtained are compared with those for the standard KP equation; some qualitative differences are found.
TL;DR: In this article, the chemistry of formation of copper sulfide and copper indium disulfide films by the chemical spray pyrolysis process has been investigated, and it was established that the formation of CuCl2 and SC(NH2)2 passes through the stage of forming intermediate complex compound Cu(SCN2H4)ClH2O in the initial solution.
Abstract: The chemistry of formation of copper sulfide and copper indium disulfide films by the chemical spray pyrolysis process has been investigated. It was established that the formation of copper sulfide films by the spray process of water solutions of CuCl2 and SC(NH2)2 passes through the stage of formation of intermediate complex compound Cu(SCN2H4)ClH2O in the initial solution. Thermal behaviour studies in air exhibit rearrangement of the complex at temperatures higher than 210 °C with formation of copper sulfide. Copper oxide is the decomposition product at temperatures higher than 700 °C in air. CuInS2 is formed by the reaction between copper and indium sulfides.
TL;DR: In this paper, the spectrum of doubly ionized zirconium Zr III was observed from 630 A to 4610 A with sliding spark discharges on the 10.7m normal-incidence vacuum spectrograph at the National Institute of Standards and Technology.
Abstract: The spectrum of doubly-ionized zirconium Zr III, was observed from 630 A to 4610 A with sliding spark discharges on the 10.7-m normal-incidence vacuum spectrograph at the National Institute of Standards and Technology. The spectral analysis of C C Kiess (1956 J. Res. Natl. Bur. Std. (US) 56 167), was considerably revised and extended. Experimental energies were obtained for almost all levels of the 4d2, 4d5s, 5s2, 4d5p, 5s5p, 4d5d, 4d6s, 4d6p, 4d4f, 5p2, 5s6s, 5s5d, 4d5f, 4d5g and 5s4f configurations as well as for a few levels of 4d7p and 4d6f. A total of 482 lines were classified as transitions between 139 energy levels. From the optimized energy level values, a system of Ritz-type wavelengths with uncertainties varying from about 0.005 A to 0.003 A was determined. The observed configurations were theoretically interpreted by means of Hartree-Fock calculations and least-squares fits of the energy parameters to the observed levels. The fitted energy parameters were used to calculate oscillator strengths and transition probabilities for all classified lines. An improved value of the ionization energy was obtained from the 4d4f, 4d5f and 4d5g configurations. The adopted value is 186 880 ± 30 cm−1 (23.170 ± 0.004 eV).