Showing papers on "Resonance published in 1978"
TL;DR: In this paper, the atomic parameter ψ2(0) and the isotropic hyperfine interaction A for unit spin density in the corresponding s orbital are calculated for the most abundant nuclei of the elements from helium to bismuth from the Hermann-Skillman wavefunction.
808 citations
01 May 1978
TL;DR: In this article, the authors have considered the interests of both scientists and practising engineers, in addition to serving the needs of the academia, in order to avoid lengthy and repetitive discussions, that are available in many standard text books on reactor physics.
Abstract: This is cne of the r-are text books written in the discipline of Nuclear Reactor Analysis, where the author has considered the interests of both scientists and practising engineers, in addition to serving the needs of the academia. The most attractive feature of this book is a balanced treatment of theory and practice of the subject matter. The theoretical foundations of the reactor design methods are explained with simplified definitions and relevant practical illustrations. The author scans through quickly the traditional aspects of the so-called reactor physics and takes the reader through the details of the analytical aspects in a conventional manner. Hcwever, there is a definite departure from the classical method of approach in order to avoid lengthy and repetitive discussions, that are available in many standard text books on reactor physics. The chief departure fran tradition is the priority accorded to the treatment of the energy part of the problems as opposed to the spatial Dart normally devoted to by other authors . A similar unorthodox approach has been applied while dealing with the solution of the various equations by giving priority to computer oriented mrethods as opposed to the classical solutions.
507 citations
423 citations
TL;DR: In this article, the wavelengths, radiative transition probabilities, and autoionization rates for ions with atomic numbers Z = 4 to 34 have been calculated for ion types with atomic number Z = 34.
375 citations
TL;DR: In this paper, a virial-scaling procedure is proposed for determining variationally optimal estimates of the resonance position and lifetime of the complex-rotated hamiltonian operators.
Abstract: The fundamental work of Balslev, Combes, and Simon has provided a mathematical foundation for the description of atomic and molecular resonances by the complex-rotation method. In the present paper we discuss some formal properties of the complex-rotated hamiltonian operators and the variational criteria for the approximation of their resonance eigenvalues. These criteria are employed in numerical studies of the complex-rotation method, which is illustrated and compared with various stabilization procedures in an application to a simple model potential. We propose a virial-scaling procedure for determining variationally optimal estimates of the resonance position and lifetime and apply the technique to the helium (2s)2 auto-ionizing resonance. Our results lend support to the idea that resonance features in the continuous spectrum can be successfully described by techniques similar to those employed for bound states.
317 citations
TL;DR: In this article, the resonance formalism of nuclear reaction theory is applied to the problem of sound scattering from submerged elastic bodies (illustrated here by circular cylinders and spheres), and it is demonstrated that the strongly fluctuating behavior of, e.g., the backscattering cross section is caused by a superposition of generally narrow resonances in the individual normal modes (partial waves), which move up in frequency from one partial wave to the next, corresponding to a series of creeping waves (Regge poles) and which are superimposed on a background of rigid-body (potential
Abstract: The resonance formalism of nuclear‐reaction theory is applied to the problem of sound scattering from submerged elastic bodies (illustrated here by circular cylinders and spheres). It is demonstrated that the strongly fluctuating behavior of, e.g., the backscattering cross section is caused by a superposition of generally narrow resonances in the individual normal modes (partial waves), which move up in frequency from one partial wave to the next, corresponding to a series of creeping waves (’’Regge poles’’), and which are superimposed on a background of rigid‐body (potential) scattering. This fact, together with a resonance representation of the elastic field in the interior, indicates that the elastic body is relatively impenetrable to the incident wave except in the vicinity of the resonances, which occur at the eigenfrequencies of the elastic vibrations of the body. Various types of interference between resonance and background are analyzed, and the phase of the partial wave is shown to undergo a jump of π at each resonance. Decay times (ringing) of the excited resonances are found to depend inversely on their width, and the appearance of nulls in the scattering angular distribution at certain resonances is related to the cross section of the rigid body.
267 citations
TL;DR: The satellite Mimas excites a trailing spiral density wave in Saturn's rings at the position of the 2:1 resonance, and the wave is damped by a combination of nonlinear and viscous effects and its negative angular momentum is transferred to the ring particles as discussed by the authors.
223 citations
TL;DR: Two-time correlations in the emissions of photons by a single atom of sodium in the presence of a coherent exciting field near resonance have been investigated in this article, where fluorescent light is collected by a microscope objective in a direction that is approximately orthogonal to both beams and imaged on two photomultipliers.
Abstract: Two-time correlations in the emissions of photons by a single atom of sodium in the presence of a coherent exciting field near resonance have been investigated. In the experiment sodium atoms in an atomic beam are excited by a perpendicular light beam from a tunable dye laser, and they are prepared by optical pumping to behave as two-level quantum systems. The fluorescent light is collected by a microscope objective in a direction that is approximately orthogonal to both beams and imaged on two photomultipliers. Photoelectric pulse correlations are measured in the presence of exciting fields of various strengths and for various detunings from the atomic resonance, and are found to exhibit significant nonclassical features. The results show clearly that the emitted photons exhibit antibunching, in good quantitative agreement with the predictions of quantum electrodynamics.
178 citations
TL;DR: In this paper, the theory of resonances is reviewed and a comprehensive review of the rigorous aspects of complex scaling is given, with references to 46 references and references from the authors of this paper.
Abstract: Certain aspects of the theory of resonances are reviewed, and a comprehensive review of the rigorous aspects of complex scaling is given. 46 references.
177 citations
TL;DR: In this paper, it was shown that for complicated ion-molecule reaction systems where a reactant ion forms N product ions, the FT ICR double resonance experiment is N times as efficient as the conventional ICR single resonance experiment.
167 citations
TL;DR: In this article, a polyisotopic sodium beam produced by reactions of 20 GeV protons in an uranium target, was illuminated with a tunable cw dye laser and analyzed by a six-pole magnet, ionized, and detected after selection of one isotope by use of a mass spectrometer.
Abstract: A polyisotopic sodium beam produced by reactions of 20 GeV protons in an uranium target, was illuminated with a tunable cw dye laser The atomic beam is analyzed by a six-pole magnet, ionized, and detected after selection of one isotope by use of a mass spectrometer From the optical ${D}_{1}$ resonance lines the hyperfine structure, magnetic moments, and isotope shifts of $^{21\ensuremath{-}31}\mathrm{Na}$ have been determined The nuclear spins of $^{26\ensuremath{-}30}\mathrm{Na}$ have been measured by magnetic resonance The results are discussed in terms of nuclear deformation The analysis of isotope shifts shows the presence of an appreciable volume shift contributionNUCLEAR STRUCTURE $^{26\ensuremath{-}30}\mathrm{Na}$; measured $J$ $^{21\ensuremath{-}31}\mathrm{Na}$; measured isotope shifts; deduced $\ensuremath{\mu}$ Atomic beam laser spectroscopy and magnetic resonance
TL;DR: In this article, the anisotropy field as measured by resonance is calculated for a coherent assembly of small magnetic particles possessing both crystal and shape anisotropic properties, and the theoretical results are compared with experimental data on precipitated cobalt and magnesioferrite particles.
Abstract: The anisotropy field as measured by resonance is calculated for a coherent assembly of small magnetic particles possessing both crystal and shape anisotropy. The theoretical results are compared with experimental data on precipitated cobalt and magnesioferrite particles.
TL;DR: In this paper, the authors derived the expression for the susceptibility of CARS by means of the usual iterative treatment of density-matrix perturbations, and then showed that this derivation can be done in a straightforward manner by using a time-ordered diagrammatic representation, which brings novel physical insight into CARS mechanisms.
Abstract: We analyze the enhancement of the coherent anti-Stokes Raman-scattering (CARS) susceptibility when the frequencies of the waves involved are tuned into resonance with discrete and continuum one-photon absorptions, and discuss the applications. We first derive the expression for the susceptibility by means of the usual iterative treatment of density-matrix perturbations. We then show that this derivation can be done in a straightforward manner by means of a time-ordered diagrammatic representation, which brings novel physical insight into CARS mechanisms. This representation can also be used to analyze the transient behavior of CARS as the pump fields are turned on and off. In addition, we discuss resonant CARS spectroscopy in the gas phase. The spectrum is composed of the expected enhanced Raman lines and also of double-electronic-resonance lines. All these lines occur as doublets. We derive their relative intensities based on detunings, collisional broadening, Franck-Condon overlap integrals, and rotational transition moments. The line contours are predicted by representing the susceptibility in the complex plane. The problems arising from saturation and the optical Stark effect are also considered; all should be small below pump densities of 100 MW/${\mathrm{cm}}^{2}$ in gas mixtures near STP. Fluorescence interference is negligible, except at power densities high enough for the Stark effect to be large. Beam absorption is also negligible at STP if the resonant species' concentration is less than 1000 ppm; phase matching is then satisfied. Finally, an experimental resonant CARS spectrum of ${\mathrm{I}}_{2}$ at 1 mb in air near STP is presented and interpreted; the susceptibility is about 400 times larger than that of ${\mathrm{O}}_{2}$ off resonance and under the same thermodynamic conditions.
TL;DR: In this article, it is shown that the "difficulties" which Bransden recently associated with the variational calculation of resonance parameters are nonexistent, provided the norm of the Gamow functions is defined appropriately and consistently.
TL;DR: In this paper, the rate constants for the reaction of N(4S) with NO have been measured from 196-400 K with two independent techniques both which utilize resonance fluoresence detection for temporal analysis of N (4S).
Abstract: Rate constants for the reaction of N(4S) with NO have been measured from 196–400 K with two independent techniques both which utilize resonance fluoresence detection for temporal analysis of N(4S). The reaction has been studied at 196, 297, and 370 K by the discharge flow‐resonance fluorescence technique (DF‐RF) and the measured rate constant is best represented by the temperature independent value of (2.7±0.4) ×10−11 cm3 molecule−1 s−1. The technique of flash photolysis‐resonance fluorescence (FP‐RF) has been used to study the reaction at 233, 298, and 400 K, and the results are best represented by the temperature independent value of (4.0±0.2) ×10−11 cm3 molecule−1 s−1. Combination of the results suggests a value of (3.4±0.9) ×10−11 cm3 molecule−1 s−1 between 196–400 K. In this work discrimination between O(3P) atom and N(4S) atom fluorescence was necessary, and this was accomplished by inclusion of an O atom resonance line filtering section as an integral part of the resonance lamp. The suggested value for the rate constant is combined with a statistical mechanical evaluation of the equilibrium constant for N(4S)+NO=N2+O(3P) to give a revised estimate for the rate constant of the back reaction. The back reaction is important in the Zeldovich mechanism for thermal production of NO in combustion systems. The rate constant is also theoretically discussed in terms of collision theory.
TL;DR: In this paper, the vibrational cross sections for vibrational excitation of ground state C2H4 and C2D4 by electron impact have been studied with a crossed-beam apparatus for electron energies between 1 and 11 eV.
Abstract: Differential cross sections for vibrational excitation of ground state C2H4 and C2D4 by electron impact have been studied with a crossed‐beam apparatus for electron energies between 1 and 11 eV. The scattering is dominated by two resonance regions in which the vibrational cross sections of totally symmetric modes are preferentially enhanced to the order of 10−16 cm2. The first resonance region is centered near 1.8 eV. Here all energy‐loss spectra and energy and angular dependences of cross sections can be accounted for by a 2B2g shape resonance of an intermediate lifetime. The second resonance region centered near 7.5 eV is very broad. The dominant vibrational modes and the corresponding angular distributions are distinctly different from those in the lower region. We interpret this second region in terms of short‐lived shape resonances, the dominant one being a 2Ag compound state comprising the target molecule plus an electron in the 4ag orbital.
TL;DR: In this article, a decay theory based on the consistent definition and calculation of the t = 0 localized state, |Ψ, is presented, where the authors deal with certain aspects of the formal properties of atomic and molecular highly excited nonstationary states and the problem of calculating their wave functions, energies and widths.
Abstract: The theory of this paper deals with certain aspects of the formal properties of atomic and molecular highly excited nonstationary states and the problem of calculating their wave functions, energies, and widths. The conceptual framework is a decay theory based on the consistent definition and calculation of the t = 0 localized state, |Ψ. Given this framework, the following topics are treated: (a) The variational calculation of Ψ0 and E0 using a previously published theory that generalized the projection operator approach to many-electron systems. (b) The exact definition of the resonance energy. (c) The possibility of bound states in the continuum. (d) The relation of Ψ0 to the resonance (Gamow) function Ψ and of the Hamiltonian to the rotated Hamiltonian H(θ) based on the notion of perturbation of boundary conditions in the asymptotic region. (e) The variational calculation of real and complex energies employing matrix elements of H and H2 with square-integrable and resonance functions. (f) The mathematical structure of the time evolution of |Ψ0〉 and the possibility of observing nonexponential decays in certain autoionizing states that are very close to the ionization threshold. (g) A many-body theory of atomic and molecular resonances that employs the coordinate rotation method.
TL;DR: In this article, the Hartree-Fock model potential for including correlation effects in relativistic Hartree Fock calculations is applied to computations of oscillator strengths for the lowest transitions in Cu I, Ag I and Au I spectra.
Abstract: The recently proposed model potential for including correlation effects in relativistic Hartree-Fock calculations is applied to computations of oscillator strengths for the lowest transitions in Cu I, Ag I and Au I spectra. The present results remove the large discrepancies between the measured fik values for resonance transitions and the values from single-configuration calculations.
TL;DR: In this article, two frequency stabilized dye lasers and a sodium atomic beam were used to study the Autler-Townes effect in the aligned 3S 1 2, F = 2, MF = 2 → 3P 3 2, F = 3, MF = 4, → 4D 5 2 and F = 4.
TL;DR: In this paper, a hot-wire method was employed to investigate the oscillating flow field in the cavity mouth, and a root locus solution of the frequency lock-in problem was obtained.
Abstract: Experimental and theoretical results are presented for a wall‐mounted cavity in turbulent flow, oscillating at Helmholtz or depth‐mode resonance, where the mouth dimensions are small compared with acoustic wavelength. A new, computerized, hot‐wire method was employed to investigate the oscillating flow field in the cavity mouth. Measured wavelength of the interface wave agrees well with predictions of Michalke, using an equivalent laminar flow model based on the oscillating mean velocity profile. By means of a forward transfer function derived from the theoretical interface wave model and a backward transfer function derived from organ‐pipe theory, a root locus solution of the frequency lock‐in problem has been obtained. Predicted frequencies and sound pressure amplitudes are in good agreement with experimental values at the lower modes. Both resonant and off‐resonant oscillation was investigated. For resonant oscillation, the streamwise slot width is required to be M−1/4 times the disturbance wavelength, where M is an integer. For situations in which the equations are applicable, the method can be used to predict design parameters for nonoscillating wall cavities in moving vessels.
TL;DR: It is demonstrated that in the fingerprint region of the resonance Raman spectrum M412 is modeled accurately by a simple unprotonated butylamine Schiff base of all-trans-retinal, and the time evolution of the M412 species and the intermediates which precede it is monitored.
Abstract: Resonance Raman spectra of various intermediates in the bacteriorhodopsin proton pumping cycle have been obtained at physiological and low temperatures. To interpret these data, spectra of model compounds, bacteriorhodopsin analogues, and isotopically labeled membranes have been measured. These results demonstrate that a protein group interacts with the Schiff base proton and, thus, the chromophore in protonated bacteriorhodopsin species is not a simple protonated Schiff base. This accounts for the abnormally low frequency of the C=N+H vibrational mode in bacteriorhodopsin and other failures to model the chromophore in bR570 with a simple butylamine protonated Schiff base of all-trans-retinal. To obtain the resonance Raman spectrum of M412 at physiological pH and temperatures, a dual beam kinetic technique was developed. We demonstrate that in the fingerprint region of the resonance Raman spectrum M412 is modeled accurately by a simple unprotonated butylamine Schiff base of all-trans-retinal. Spectral resolution and the solution environment of the membrane suspensions play important roles in this conclusion. Kinetic resonance Raman techniques are also used to monitor the time evolution of the M412 species and the intermediates which precede it. We find spectral features in our kinetic data which can be assigned to L550, and we present evidence for a new unprotonated species (X) which occurs before M412. Single pass flow resonance Raman spectra of bR560 also have been obtained, and, although bR570 and M412 appear to have all-trans chromophores, there are 13-cis-like features in the spectra of bR560, L550, and X.
TL;DR: In this article, a Stieltjes-moment-theory-based method was proposed for calculating the widths of atomic and molecular resonances, using only square-integrable functions to approximate the nonresonant scattering solutions.
Abstract: A new method is proposed for calculating the widths of atomic and molecular resonances. The method uses only square-integrable functions to approximate the nonresonant scattering solutions and employs Stieltjes-moment-theory techniques to extract a continuous approximation for Gamma (E) from a discrete representation of the background continuum. The method has been applied to several well known resonances in He, He- and Mg- with encouraging results. The proposed method is easily applied to molecular problems.
TL;DR: Theoretical calculations show that rotational coupling, Fermi resonance, Coriolis coupling, and resonance energy transfer can strongly effect the vibrational population lifetime as discussed by the authors, and the relevance of these processes is quite different for the various molecules investigated.
TL;DR: In this paper, the authors used laser magnetic resonance to detect the hydroperoxyl radical HO2 in the ν3 fundamental band (0-0 stretch; ν0=1097.626 cm−1).
Abstract: The ν3 fundamental band (0–0 stretch; ν0=1097.626 cm−1) of the hydroperoxyl radical HO2 has been studied using the technique of laser magnetic resonance, in which molecular transitions are tuned into resonance with fixed laser lines by means of the Zeeman effect. The HO2 was produced by reacting O atoms with methyl or allyl alcohol in a flow system incorporating an absorption cell inside the CO2 laser cavity. Over 200 resonances involving different MJ components of a‐type HO2 transitions with 1⩽N⩽7 and 0⩽Ka⩽4 were assigned, and from an analysis of the spectra the band origin and excited state rotational, centrifugal distortion, and spin–rotation interaction parameters were determined. The possible application of these results to the remote spectroscopic detection of HO2 is discussed.