Search

An extended calculation of energy levels, radiative rates, and lifetimes are reported for sodium-like chromium. Extensive configuration interaction calculations have been performed using general-purpose relativistic atomic structure package (GRASP). The radiative rates, oscillator strengths, and line strengths are listed for all electric dipole (E1) transitions. However, for magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions, only radiative rates are listed. The importance of valence–valence (VV) and core–valence (CV) correlation effects in the calculation of energy levels have also been shown. To confirm the accuracy of the present results for energy levels by GRASP, independent calculations have been performed by using Flexible Atomic Code (FAC) and configuration interaction method (CIV3). The accuracy of the present levels, wavelengths, transition rates, and lifetimes are assessed by comparing them to available experimental and other theoretical results. We believe that our extensive results may be beneficial in fusion plasma research and astrophysical investigations and applications.

Extensive and elaborate theoretical computations of Cu XIX have been performed by employing multi-configuration Dirac-Fock (MCDF) method. We have presented energy levels and radiative data such as, transition wavelengths, radiative rates, oscillator strengths and line strengths for electric dipole (E1) transitions in Na-like Cu. For other types of transitions, namely magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2), only the A-values are listed. We have also discussed the importance and the effect of valence-valence (VV) and core-valence (CV) correlations on the excitation energies in graphical as well as in tabular form. The accuracies of the presented levels, wavelengths, transition rates and lifetimes are assessed by comparing them to available experimental and other theoretical results. Analogous calculations have been carried out by using Flexible Atomic Code (FAC) based on self-consistent Dirac-Fock-Slater iteration method. QED corrections due to vacuum polarization and self-energy effects, and Breit correction due to the exchange of virtual photons between two electrons are fully considered and their effects on the energy levels are studied graphically. The fine-structure energy levels have also been reported by using the Configuration Interaction (CIV3) technique. An intercomparison among three independent calculations helps us in assessing the credibility and integrity of our reported data. Additionally, we have shown the variation of the line intensity ratios and electron density with plasma temperature graphically for Cu XIX. We have also identified Extreme Ultraviolet (EUV) and Soft X-ray (SXR) transitions and believe that our reported results may be beneficial in space and laboratory plasma research.

Electron impact excitation collision strengths for the transitions among the lowest twelve fine structure levels belonging to $$2\hbox {p}^{\mathrm {6}}\hbox {nl }$$ ( $$\hbox {\textit{n}}=3,4,\hbox {\textit{l}}=0-3$$ ) configurations of Cu XIX ion are presented using the close-coupling Breit–Pauli R-matrix method. Target state wavefunctions have been constructed using the AUTOSTRUCTURE. The collision strengths are also tabulated at selected energies above the excitation thresholds in the range 50–300 Ryd. For assessing the accuracy and reliability of our collision strength values, an independent calculation has been carried out using the relativistic distorted wave method. The effective collision strengths are obtained over a wide electron temperature range of $$1.0\times 10^{\mathrm {5}} - 4.0\times 10^{\mathrm {7}}$$ K by averaging over a Maxwellian distribution of velocities. We believe that our present results will be beneficial in the modelling of astrophysical and fusion plasmas.

Plasma shielding effects on the energy levels and radiative properties of He-like Ca\(^{18+}\) ion under dense plasma conditions have been studied. For this purpose, the multiconfiguration Dirac-Fock method has been implemented by incorporating the ion sphere model potential as a modified interaction potential between the electron and the nucleus. To check the authenticity of our results, independent calculations have been performed using the modified relativistic configuration interaction method. It is observed that the transition energies associated with \(\Delta n = 0\) transitions are blue shifted, whereas red shifted for \(\Delta n \neq 0\) transitions. The variation in transition probabilities and weighted oscillator strengths with plasma densities has also been analyzed. The present results should be beneficial in the plasma modeling and fusion plasma research applications.

The total photoionization cross sections for the ground state 2p63s2(1S0) and the lowest three excited states 2p63s3p(3Po0,1,2) of the Mg-like Cu XVIII ion have been calculated by making use of the close-coupling Breit Pauli R-matrix (BPRM) approximation. The lowest 21 target level states of Cu XIX have been included in the photoionization calculations of Cu XVIII. Our calculated target state energies of the core ion Cu XIX show a good agreement with the observed energies tabulated in the NIST database. To further assess the accuracy of our BPRM results, photoionization cross section calculations for the ground state configuration have also been performed by employing the fully relativistic Dirac atomic R-matrix code (DARC). Our two independent calculations show a reasonable agreement between the calculated cross sections in the overall background shape and magnitude. We believe that our cross section data may be beneficial for the modelling and diagnostics of astrophysical and laboratory plasmas.

The ITER Electron Cyclotron Emission (ECE) diagnostic is progressing towards its Preliminary Design Review (PDR). In parallel, the diagnostic integration in the Equatorial Port is ongoing. Port Integration has to address the structural integrity to withstand various loads, maintenance and the safety aspects of ECE diagnostic. The ITER ECE system includes radial and oblique lines-of-sight. Recently, a successful peer-review of the in-port plug Hot Calibration Source has taken place and its performance and integration feasibility has been demonstrated. Four 45-meter long low-loss transmission lines are designed to transmit mm-wave power in the frequency range of 70- 1000 GHz in both X- and O-mode polarization from the port plug to the ECE instrumentation room in the diagnostic building. Prototype transmission lines are being tested [1]. A prototype polarizing Martin-Puplett type Fourier Transform Spectrometer (FTS) operating in the frequency range 70-1000 GHz, has a fast scanning mechanism and a cryo-cooled dual-channel THz detector system. Its performance has been tested as per ITER requirements. Assessment of the instrumentation and control requirements, functional and non-functional requirements, operation procedures, plant automation are ongoing for the PDR. The current status of the diagnostic, together with integration activities, is presented.

This paper investigates BER performance of freespace optical (FSO) communication over strong turbulence channel together with pointing errors effects. Take atmospheric attenuation, atmospheric turbulence and pointing errors into account, a statistical model for the optical intensity fluctuation at the receiver is described. For given weather and misalignment conditions, a closed-form expression is derived for BER performance of FSO communication system. Moreover, the simulation results show that the closed-form expression can provide sufficient precision for evaluating BER performance of FSO communication systems.

The influence of plasma screening on the transition energies and radiative properties of He-like ions embedded in dense plasma environment has been analyzed. For this purpose, the multiconfiguration Dirac-Fock method and Flexible Atomic Code incorporating the analytical plasma screening potential of Li et al. (2019) [39] and uniform electron gas model potential have been implemented. Our calculated line shifts of 1 s 2 S 0 1 → 1 s 3 p P 1 o 1 He-β transition of Cl15+ are in excellent agreement with the recent measurements of Beiersdorfer et al. (2019) [11] . The plasma shielding effects on 1 s 2 S 0 1 → 1 s n p P 1 o 3 ( n = 2 , 3 ) and 1 s 2 S 0 1 → 1 s n p P 1 o 1 ( n = 2 , 3 ) transitions of Ar16+, Ti20+ and Fe24+ ions have also been studied. It is found that transition energies for these transitions are red shifted with respect to free electron densities. The present results should be advantageous in the modeling and diagnostics of laboratory and astrophysical plasmas.

Photoionization cross sections of the ground state 2p63s2 (1S0) and the first three excited states 2p63s3p (3Po0,1,2) of Mg-like Se XXIII have been reported by employing the fully relativistic Dirac atomic R-matrix code (DARC). For construction of target wavefunctions, multiconfiguration Dirac-Fock calculations are performed for the lowest 21 fine structure energy levels belonging to 2p6nl (3 ≤ n ≤ 5) configurations. Our calculated target state energies of the core ion Se XXIV show close agreement with the energies tabulated in the NIST database. In order to assess the accuracy of our DARC results, photoionization cross section calculations of the ground state configuration have also been performed using the close-coupling Breit-Pauli R-matrix (BPRM) method. Our two independent calculations show a good agreement both in magnitude and resonant photoionization cross sections. The resonance energies (Er) and widths (Γ) of the 3pns (3P1,1P1), 3pnd (3D1, 3P1, 1P1), 3dnp (3D1, 3P1, 1P1) and 3dnf (3D1, 3P1, 1P1) series due to ejection of a 3s electron from the ground state 2p63s2 (1S0) have also been predicted by adopting Quigley and Berrington (QB) method. We believe that our results might be beneficial for the modelling and diagnostics of fusion and laser generated plasmas.

Aluminium is a third group element according to the periodic table. Chemically it is a reactive metal often forming complexes within its binary alloys. In the present work we have dealt with the impact of eigenvalues on the superconducting state parameter viz. the electron-phonon coupling strength of this metal. We have also dealt with the same for two binary alloys of it viz. aluminium-magnesium and aluminium-zinc. For this purpose we have computed the non-local screened form factor for each of them. Initially the orthogonalised plane wave parameter has been taken as unity. Thereafter Vashishta-Singwi form of exchange and correlation is employed. The core energy eigenvalues of Herman-Skillman have been used. Our results are quite satisfactory for the metal as well as its present alloys. Our computation reveals that the superconducting state parameter can be reasonably reproduced by Harrison’s first principle pseudopotential technique along with McMillan’s formalism provided a proper choice of the core energy eigenvalues is made.DOI: http://dx.doi.org/10.3126/bibechana.v12i0.11699BIBECHANA 12 (2015) 35-39

Extensive calculations of energy levels and radiative data such as transition wavelengths, radiative rates, oscillator strengths, and line strengths for electric dipole (E1) transitions have been performed for Se XXIV using the multiconfiguration Dirac–Fock method. For other types of transitions, namely, magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2), only the radiative rates (A) are listed. The importance and effect of valence-valence and core-valence correlations on the excitation energies have been studied. For additional accuracy assessments, analogous calculations have been carried out by employing the flexible atomic code and configuration interaction technique. Comparisons are made with the available experimental and theoretical data in the literature. Close agreement has been found ensuring the accuracy and reliability of our results. The effect of plasma temperature on the line intensity ratio, electron density, plasma frequency, and skin depth has been analyzed for hot dense plasma (HDP) in local thermodynamic equilibrium. The present work might be beneficial in the modeling and characterization of HDP.Extensive calculations of energy levels and radiative data such as transition wavelengths, radiative rates, oscillator strengths, and line strengths for electric dipole (E1) transitions have been performed for Se XXIV using the multiconfiguration Dirac–Fock method. For other types of transitions, namely, magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2), only the radiative rates (A) are listed. The importance and effect of valence-valence and core-valence correlations on the excitation energies have been studied. For additional accuracy assessments, analogous calculations have been carried out by employing the flexible atomic code and configuration interaction technique. Comparisons are made with the available experimental and theoretical data in the literature. Close agreement has been found ensuring the accuracy and reliability of our results. The effect of plasma temperature on the line intensity ratio, electron density, plasma frequency, and skin depth has been analyzed for ...

Energies, lifetimes, and wavefunction compositions have been computed for all levels of odd parity 4s24p5 ground configuration and 3d94s24p6 excited configuration as well as 4s4p6 and 4s24p44d even parity excited configurations in highly charged Br-like tungsten ion (W XL) by using the multiconfigurational Dirac–Fock method. Also, we have reported the transition wavelengths, oscillator strengths, transition probabilities and line strengths for the electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transition from the 4s24p5 configuration. We have compared our calculated results with the other available experimental and theoretical results. The excellent agreement observed between our new results and those obtained using different approaches confirm the quality of our results.

Semi-relativistic calculations are performed for the photoionization of Fe X (an important coronal ion) from its ground state 3s23p $^{5}(^{2}P^{0}_{3/2})$ and the first two excited states 3s23p $^{5}(^{2}P^{0}_{1/2})$ and 3s3p $^{6}(^{2}S_{1/2})$ using the Breit–Pauli R-matrix method. A lowest 41 state eigenfunction expansion for Fe XI is employed to ensure an extensive treatment of auto ionizing resonances that affect the effective cross-sections. In the present calculations, we have considered all the important physical effects like channel coupling, exchange and short range correlation. The present calculations using the lowest 41 target levels of Fe XI in the LSJ coupling scheme are reported and we expect that the present results should enable more accurate modelling of the emission spectrum of highly excited plasma from the optical to the far UV region.

A large-scale configuration interaction (CI) calculation using CIV3 is performed for the 303 fine-structure levels of the aluminum-like titanium ion. We have calculated the energy levels, oscillator strengths, and transition probabilities for the electric dipole allowed and intercombination transitions among the levels of ground state 3s 2 3p ( 2 p o ) and higher energy levels of states 3s3p 2 , 3p 3 , 3s3p3d, 3p 2 3d, 3s 2 4s, 3s3d 2 , 3s 2 4p, 3s3p4s, 3s3p4p, 3p3d 2 , 3s3p4d, 3s3p4f, 3s 2 5p, 3p 2 4p, 3s3d4s, 3s3p5s, 3s3d4p, 3s3p5p, 3s 2 (4d, 4f, 5s, 5d, 5f, 6s, 6p, 6d, 6f) of Ti X in the LSJ coupling scheme. The calculations include all the major correlation effects. We attempt to correct the inaccuracies in the CI coefficients in the wavefunctions, which would lead to inaccuracies in transition probabilities by applying a “fine-tuning” technique. The relativistic effects are incorporated by adding the mass correction, Darwin, and spin–orbit interaction terms into the non-relativistic Hamiltonian in the Breit–Pauli approximation. The present results are in good agreement with other available calculations and experiments. Several new lines corresponding to 3s3p nl ( n = 4, 5 and l = 0, 1), 3s 2 5p, 3s 2 (6s, 6p) and other configurations are predicted where no other theoretical or experimental results are available. We expect that our extensive calculations will be useful to experimentalists in identifying the fine-structure levels in their future work.

We present relativistic close-coupling photoionization calculations of Ni XV using the Breit-Pauli R-matrix method to obtain photoionization cross section of Ni XV from the ground state 3s 23p 2(3 P 0) and the lowest four 3s 23p 2 (3 P 1,2, 1 D 2, 1 S 0) excited states. A multiconfiguration eigenfunction expansion of the core Ni XVI is employed with configurations 3s 23p, 3s3p 2, 3s 23d, 3p 3, 3s3p3d, 3p 23d, 3s3d 2, 3p3d 2. We have included the lowest 40 target level states of Ni XVI in the photoionization calculations of Ni XV. Cross sections are determined by the Rydberg series of autoionizing resonances converging to several ionic states of Ni XVI. In our calculations, we have taken into account all the important physical effects such as exchange, channel coupling, and short-range correlation. Further, relativistic effects are incorporated by including mass correction, Darwin term, and spin-orbit interaction terms. The present calculations using the lowest 40 target levels of Ni XVI are presented for the first time and can be useful for modeling the ionization balance of Ni XV in laboratory and astrophysical plasmas.

The relativistic R-matrix method is used to calculate photoionization cross section for the ground state 1s22s22p6 1Se (J = 0) and the first four excited states (J = 0 even) of Ne-like Ni XIX, using the lowest 68 target states of Ni XX. Cross sections are dominated by Rydberg series of autoionizing resonances converging to several ionic states. We have compared our new 68-level cross sections with 32-level and with much lower 3-levels calculations. The 3-level results are found to be inadequate for practical applications due to the lack of complete set of resonances converging at higher thresholds. In our calculations, we have taken all the important physical effects like exchange, channel coupling, and short-range correlation, as well as relativistic effects into account. Our present results can be useful for modeling ionization balance of Ni XIX in laboratory and astrophysical plasmas. We believe that this is the first relativistic calculation for this ion to obtain the photoionization cross section.

Electron excitation collision strengths for the transitions from the ground state to the fine-structure levels of the 3s23p53d and 3s23p63d configurations in Ni XI are calculated using the Breit-Pauli R-matrix method. Configuration interaction wavefunctions have been used to represent the target states. The relativistic effects are incorporated in the Breit-Pauli approximation by including one-body mass correction, Darwin, and spin-orbit interaction terms in the scattering equations. Collision strengths are tabulated at selected energies in the range 10 to 75 Rydberg. Effective collision strengths are determined by integrating collision strengths by assuming a Maxwellian distribution of electron energies. The effective collision strengths are listed over a wide temperature range (2×104-1×107 K) applicable to astrophysical plasmas. Our results are the only collision strengths and effective collision strengths available for this ion. We believe that the data calculated in this work will be useful in solar, astrophysical and laser applications.

We present an extensive, ab initio configuration interaction calculation of oscillator strengths, transition probabilities, and lifetimes of the upper levels of all transitions in Ti VI between the levels of 3s23p5, 3s3p6, 3p43d, 3p44s, 3p44p and 3p44d states in the LSJ coupling scheme. Relativistic effects are incorporated by adding the mass correction, Darwin, and spin–orbit interaction terms to the non-relativistic Hamiltonian in the Breit–Pauli approximation. The calculations incorporate the major correlation effects. The calculated energy levels are in close agreement with most of the NIST tabulation. However, some discrepancies in the energy positions with experimental energies occur in levels with 3p43d 1D and 3P cores, particularly belonging to 2P and 2D symmetries. We predict new data for several levels where no other theoretical and/or experimental results are available. Our extensive calculations will be useful to experimentalists in identifying the fine-structure levels in their future work.

In this letter we show the effect of rotation of two oscillators on the sensitivity performance of two SAW coupled oscillator sensor configuration. The dependence of synchronization frequencies on the frequency detuning between the two counter-rotating oscillators, the insertion loss and delay of the coupling SAW delay line are analysed. The sensitivity for SAW coupled counter-rotating oscillators system is compared with SAW coupled co-rotating oscillator system for the similar range of system parameters to understand the effect of rotation of oscillators. The preliminary analyses show that the rotation direction of the two oscillators in a SAW coupled oscillators system emerges several interesting features to make this system more appropriate for sensor applications.

The close-coupling R-matrix method has been used to calculate photoionization cross sections for the ground and the lowest three excited states using the relativistic Breit–Pauli approximation. Configuration interaction wave-functions are used to represent eleven lowest LSJ target states of Si VI retained in the R-matrix expansion. Relativistic effects are clearly revealed from resonance converging on the excited states of Si VI.PACS No.: 32.80.Fb

We present relativistic close-coupling photoionization calculations of Al IV using the Breit-Pauli R-matrix method to obtain photoionization cross-section of Al IV from the ground state and the lowest two J=0 (even) excited states. A multi-configuration eigenfunctions expansion of the core Al V is employed with spectroscopic configurations 2s22p5, 2s2p6, 2s22p43s, 2s22p43p, 2s22p43d and 2s22p44s. We have included, for the first time, the lowest 68 level target states of Al V in the photoionization calculations of Al IV. Extensive configuration interaction wavefunctions are used to describe both the initial Al IV states and the final Al V states. Cross-sections are compared from three level calculations including only 2s2 2p5 2Po 3/2, 1/2 and 2s 2p6 2S1/2 levels of Al V. The present calculation using the lowest 68 target levels of Al V are presented for the first time and should provide reasonably complete database for practical application for photoionization cross-section for Al IV, where high-energy cross-sections along with near-threshold photoionization cross-section is required.

Semi-relativistic calculations are carried out for the photoionization of neutral argon from its ground state 3s23p61S0 and the lowest three excited levels 3s23p5(2P0)4s3P02, 3s23p5(2P0)4s 3P01 and 3s23p5(2P0)4s 3P00, using the semi-relativistic Breit–Pauli approximation. Configuration interaction (CI) wavefunctions are used to represent the lowest 12 target states of the Ar II ion retained in the R-matrix expansion. The Rydberg series 3s3p6 2S1/2{np[1/2]1, np[3/2]1}, J=1° of autoionizing resonances formed in the photoionization process of ground state 3s23p61S0, just below 3s3p6 2S1/2 threshold of Ar II, are identified and their resonance positions and effective quantum numbers are reported. Excellent agreement with previously published resonance positions and effective quantum numbers is observed. Further, new results for photoionization cross-sections from excited states of Ar, involving clusters of Feshbach resonances converging to different thresholds of Ar II, are predicted.

A large-scale configuration interaction (CI) calculation using Program CIV3 of Hibbert is performed for the lowest 87 fine-structure levels of argon-like iron ions. We have calculated energy levels, oscillator strengths, and transition probabilities for all electric-dipole-allowed and intercombination transitions between the levels of 3s23p6, 3s23p53d, 3s3p63d, 3s23p54s, 3s23p54p, 3s23p54d, 3s3p64s, 3s23p54f, 3s3p64p, 3s23p55s, 3s23p55p, and 3s23p55d states of Fe IX in the LSJ coupling scheme. Lifetimes of the 3d levels are also determined. The calculations include the major correlation effects. We attempt to correct the inaccuracies in the CI coefficients in the wave functions, which would lead to inaccuracy in transition probabilities by applying a "fine-tuning" technique. The relativistic effects are incorporated by adding mass correction, Darwin term, and spin-orbit interaction terms to the nonrelativistic Hamiltonian in the Breit-Pauli approximations. The present results are in good agreement with other available calculations and experiments. We predict new data for several levels where no other theoretical or experimental results are available. We hope our extensive calculations will be useful to experimentalists in identifying the fine-structure levels in their future work.

Breit-Pauli Energy levels, oscillator strengths and transition probabilities for all the transitions in Cl I between the fine structure levels of 3s2 3p5, 3s2 3p43d, 3s2 3p44s and 3s23p44p states are calculated using extensive configuration interaction (CI) wave functions. We have also determined the lifetimes of 3s2 3p43d, 3s2 3p44s and 3s2 3p44p levels. The relativistic effects are included through Breit-Pauli approximation via spin-orbit, Darwin and mass correction terms. Prior to the calculations of the oscillator strengths and transition probabilities, we fine-tune the CI coefficient using experimental energies. Our results are compared with experimental and other available theoretical data. The calculated energy levels are in close agreement with most of the NIST compiled data. We predict new lifetime data for several levels where no other theoretical and/or experimental results are available, which will form the basis for the future experimental work.

Large-scale configuration interaction (CI) calculations are performed to evaluate the energy levels, oscillator strengths and transition probabilities for all the transitions in Co XI from ground-state level to those of 3s3p6, 3s23p43d, 3s23p44s and 3s23p44d states in LSJ coupling scheme. Lifetimes of the 3s3p6 and 3s23p43d levels are also determined. The calculations include the major correlation effects. We attempt to correct the inaccuracies in the CI coefficients in the wavefunctions, which would lead to inaccuracy in transition probabilities by applying a 'fine-tuning' technique. The relativistic effects are incorporated by adding mass correction, Darwin term and spin–orbit interaction terms to the non-relativistic Hamiltonian in the Breit–Pauli approximations. The calculated energy levels are in close agreement with the NIST results. We have predicted many new spectral lines, which are to be experimentally observed in the future.

We have done relativistic calculations for the evaluation of energy levels, oscillator strengths, transition probabilities and lifetimes for Cr VIII ion. Use has been made of configuration interaction technique by including Briet-Pauli approximation. The energies of various levels from the ground state to excited levels of 3s3p6, 3s23p43d, 3s23p44s, 3s23p44d of Cr VIII are given in LSJ coupling scheme after fine-tuning and are compared with the experimental results compiled in the NIST Data Base. Many new lines have been predicted which have not appeared so far in the NIST Data.

Using the general formulation for obtaining chemical potentialμ of an ideal Fermi gas of particles at temperature T, with particle rest mass m0 and average density 〈N〉/V, the dependence of the mean square number fluctuation 〈ΔN 2〉/V on the particle mass m0 has been calculated explicitly. The numerical calculations are exact in all cases whether rest mass energym 0c2 is very large (non-relativistic case), very small (ultra-relativistic case) or of the same order as the thermal energy kBT. Application of our results to the detection of the universal very low energy cosmic neutrino background (CNB), from any of the three species of neutrinos, shows that it is possible to estimate the neutrino mass of these species if from approximate experimental measurements of their momentum distribution one can extract, someday, not only the density 〈N v〉/V but also the mean square fluctuation 〈Δ v 2 〉/V. If at the present epoch, the universe is expanding much faster than thermalization rate for CNB, it is shown that our analysis leads to a scaled neutrino massm v instead of the actual massm 0v .

A general theory is presented to describe optomechanical interactions of acoustic phonons, having extremely long lifetimes in superfluid $^{4}\mathrm{He}$, with optical photons in the medium placed in a suitable electromagnetic cavity. The acoustic nonlinearity in the fluid motion is included to consider processes beyond the usual linear process involving the absorption or emission of one phonon at a time. We first apply our formulation to the simplest one-phonon process involving the usual resonant anti-Stokes upconversion of an incident optical mode. However, when the allowed optical cavity modes are such that there is no single-phonon mode in the superfluid, which can give rise to a resonant allowed anti-Stokes mode, we must consider the possibility of two-phonon upconversion. For such a case, we show that the two-step two-phonon process could be dominant. We present arguments for a large two-step process and negligible single-step two-phonon contribution. The two-step process also shows interesting quantum interference among different transition pathways.

Electromagnetic wave consists of an electric field and a magnetic field at right angles to each other and to the direction of the motion of the wave. Frequency and wavelength characterize an electromagnetic field. In an electromagnetic wave, these two characteristics are directly related to each other: the higher the frequency the shorter the wavelength. ELF fields generally have frequencies up to 300 Hz. Other technologies produce intermediate frequency (IF) fields with frequencies from 300 Hz to 10 MHz and radiofrequency (RF) fields with frequencies of 10 MHz to 300 GHz. The effects of electromagnetic fields on the human body depend not only on their field level but on their frequency and energy. These fields are required to be limited to the prescribed values in the respective frequency ranges in order to avoid the effects such as heating and electric shock.

Anisotropy and the wave-vector dependence of the energy gap function determine many important properties of a superconductor. Starting from first principles, we present here a complete analysis of possible symmetries of the superconducting gap function E{sub g}({bold k}) at the Fermi surface in high-T{sub c} layered superconductors with either a simple orthorhombic or a tetragonal unit cell. This is done within the framework of Gorkov{close_quote}s mean-field theory of superconductivity in the so-called {open_quotes}layer representation{close_quotes} introduced by us earlier. For N conducting cuprate layers, J=1,2,{hor_ellipsis},N, in each unit cell, the spin-singlet order parameters {Delta}{sub JJ}({bold k}) can be expanded in terms of possible basis functions of all the irreducible representations relevant to layered crystals, which are obtained here. In layered materials, the symmetry is restricted to the translational lattice periodicity in the direction perpendicular to the layers and the residual point group and translational symmetries for the two-dimensional unit cell in each layer of the three-dimensional unit cell. We derive an exact general relation to determine different branches of the energy gap function E{sub g}({bold k}) at the Fermi surface in terms of {Delta}{sub JJ}({bold k}), which include both intralayer and interlayer order parameters. For N=2, we also obtain an exactmore » expression for quasiparticle energies E{sub p}({bold k}), p=1,2, in the superconducting state in the presence of intralayer and complex interlayer order parameters as well as complex tunneling matrix elements between the two layers in the unit cell, which need not be equivalent. The form of the possible basis functions are also listed in terms of cylindrical coordinates k{sub t},{phi},k{sub z} to take advantage of the orthogonality of functions with respect to {phi} integrations. (Abstract Truncated)« less

We discuss the possible cooling of different phonon modes via three-wave mixing interactions of vibrational and optical modes. Since phonon modes exhibit a variety of dispersion relations or frequency spectra with diverse spatial structures, depending on the shape and size of the sample, we formulate our theory in terms of relevant spatial mode functions for the interacting fields in any given geometry. Our general formulation is applicable to cooling of any low-frequency excitation mode in matter which can give appreciable inelastic light scattering via the modulation of the optical dielectric function. We discuss the possibility of Dicke-like collective effects in phonon cooling and present explicit results for simultaneous cooling of two-phonon modes via the anti-Stokes up-conversions. We show that the bimodal cooling should be observable experimentally.

The wave-vector dependence of superconducting order parameters and the corresponding transition temperature in three-dimensional layered metals are investigated. It includes planar anisotropic {ital s}-wave-like as well as {ital d}-wave-like pairing contributions, but for simplicity only intralayer pairing of electrons has been considered for tetragonal and orthorhombic crystal structures, relevant to high-{ital T}{sub {ital c}} materials. It is shown that for the orthorhombic case order parameters are likely to have mixed symmetry, whereas in tetragonal structures it is possible to have only planar {ital d}-wave-like symmetry with a possible correction term with an additional wave-vector dependence in the direction perpendicular to the reciprocal layer plane. {copyright} {ital 1996 The American Physical Society.}

We present near infra-red light curves of supernova (SN) 2011fe in M101, including 34 epochs in H band starting fourteen days before maximum brightness in the B-band. The light curve data were obtained with the WIYN High-Resolution Infrared Camera (WHIRC). When the data are calibrated using templates of other Type Ia SNe, we derive an apparent H-band magnitude at the epoch of B-band maximum of 10.85 \pm 0.04. This implies a distance modulus for M101 that ranges from 28.86 to 29.17 mag, depending on which absolute calibration for Type Ia SNe is used., 9 pages, 3 figures, emulateapj style, accepted for publication in The Astrophysical Journal

The structure of the general effective pairing interaction V(r 1 ,r 2 ;ω) for spin-singlet superconductivity in layered systems is examined in detail in a layer representation for the single-particle states. This interaction, averaged over the layer-plane momentum transfers near the Fermi surface [i.e., pp V‾(q,q';ω)], is expressed in terms of intracell-intralayer, intracell-interlayer, intercell-intralayer, and intercell-interlayer couplings, where q,q' are wave vectors in the direction of the normal to the layers. In our general picture, because of the interaction process, a localized particle can scatter across from one layer to another in the same unit cell, as well as from one vertical unit cell to another cell. The dominant coupling terms are due to the interaction of two particles localized on layers within the same vertical unit cell, both before and after the scattering. The intercell coupling terms correspond to scattering processes in which at least one of the particles is localized in a different vertical unit cell either before or after the scattering. Whereas the ratio δ c between the intracell and nearest-neighbor intercell couplings is assumed to be small compared with unity in our analysis, no perturbative approach is used to distinguish the magnitudes of interlayer couplings from the corresponding intralayer couplings. General results for T c and the superconducting-order-parameter matrix Δ, are discussed for the case of N layers per unit cell, both in the limit in which the off-diagonal tunneling terms, t(q), appearing in the inverse of the normal-state single-particle N×N Green-function matrix, g -1 , in the layer representation, are either neglected or included to the lowest order in ||t(q)||/μ. Here, μ is the chemical potential. We find that the q,q' dependence of pp V arises only from intercell couplings which in turn implies that the q dependence and anisotropy in Δ are entirely due to intercell interactions. Explicit results are given for T c as well as the order parameters for the case of N=1 and 2, to leading orders in δ c and ||t(q)||/μ. We find that anisotropy in the gap parameter in the layer representation always arises due to the intercell interactions, and is present even in the N=1 case. It is also found that the presence of interlayer couplings tends to enhance T c in general. In a representation in which g -1 is diagonal, called the α-band representation here, we reformulate the problem in terms of new order parameters, Δ(α) and new effective interaction, pp V(α)(qq';ω). Although, in this representation there appear additional q,q' dependences in pp V (α) , these do not imply extra anisotropy in the corresponding gap parameter Δ in the layer representation. This is only an artifact of the use of the a representation as revealed by the relation between Δ(α) and Δ. For interband pairing in the α representation, we also present a complete calculation for the resulting order parameter.

We show that the comment of K.M. Aggarwal (Can. J. Phys. 92, This issue. (2014) doi:10.1139/cjp-2013-0382 ), although being only marginally relevant to the content of the original paper (Can. J. Phys. 91, 394 (2013)), misinterprets our results and leads to a wrong conclusion.

We show that the ground state of a system of magnetic dipoles, with no electric charge, is a ferromagnetic quantum Fermi liquid at high densities, driven by the dipolar exchange energy. As in the system of classical point dipoles, the direct dipole energy is zero in this case. With decreasing density, there is a transition to an antiferromagnetic lattice state. An addition of short range hard core repulsive potential will arrest the infinite density collapse of the ferromagnetic state, and possible melting of the low density antiferromagnetic lattice state.

A theoretical framework for treating the effects of magnetic fieldH on the pairing theory of superconductivity is considered, where the field is taken in an arbitrary direction with respect to crystal axes. This is applicable to closed, as well as open normal state Fermi surface (FS), including simple layered metals. The orbital effects of the magnetic field are treated semiclassically while retaining the full anisotropic paramagnetic contribution. Explicit calculations are presented in the limits |H| → |Hc2(T)|,T ∼ 0 andT →Tc(|H|), |H| ∼ 0. Effects of weak nonmagnetic impurity scattering, without vertex corrections, have also been taken into account in a phenomenological way. The final results for the case of open FS and layered materials are found to differ considerably from those of the closed FS. For example, an important parameter,h(T=0)=|Hc2(0)|/[-Tδ|Hc2T|δT]T{s0} for the case of a FS open inkz-direction with thekz-bandwidth, 4t3, very small compared to the Fermi energy,EF, is close to 0.5906, compared to 0.7273 for the closed FS, in the clean limit. Analytical results are given for the magnetic field dependence ofTc and the temperature dependence of Hc2 for a model of layered superconductors with widely open FS. For a set of band structure parameters for YBa2Cu3O7 used elsewhere, we find reasonable values for the upper critical fieldHc2(0), the slope (dHc2/dT)Tc0, anisotropic coherence lengths ζi(T=0),i=x, y, z, and (dTc/d|H|)|H| → 0.

We calculate the intraband electronic Raman scattering cross section from charge density fluctuations of holes in YBCO and the real part of the transverse electromagnetic conductivity in the normal state, using phenomenological linear frequency-dependent collision rates ω c (ω, T ). Whereas there is a general agreement with the experimental data on infrared conductivity, we are unable to obtain the extent of flatness of the electronic Raman continuum as observed in several experiments.

The intraband electronic Raman scattering cross-section from charge-density fluctuations of holes in YBCO has been calculated, along with their longitudinal and transverse dielectric response functions. A consistent set of electronic parameters for a simple anisotropic model of the single-particle hole energy and the normal-state collision frequency ωc(ω, T) has been chosen in a way that leads to the observed DC and optical conductivities. Because the band-width, 2t3, perpendicular to the a-b plane is much smaller than the Fermi energy μ in such a layered material, the Fermi surface is assumed to be open in the kz-direction. It is taken to be almost circular in the kx-ky plane, but the nonparabolicity of the band is retained while calculating the unscreened part of the single-particle scattering cross-section. We show that it is possible to obtain a flat electronic Raman spectrum due to highly damped plasmon excitations, only in the extreme collision-dominated regime. Within the same model, the nature of the transverse and longitudinal dielectric tensors, and the form of the electronic part of the attractive dynamic pairing interaction, (4πe2/q2) [(1/ϵ(q, ω))-1], beyond the repulsive static Coulomb interaction, are also discussed.

We study the nature of the electromagnetic absorption in a superconductor with an anisotropic energy gap and a nonspherical Fermi surface that is either completely closed or open along the direction of the c axis of the crystal. The real part of the electromagnetic conductivity σ μν (q,ω) has been calculated for a wide range of the normal-state collision frequency ω c and the parameter Q=max{||q.V F ||}, where q is the incident wave vector of the electromagnetic wave and V F is quasiparticle velocity at the Fermi surface. For simplicity, the model gap parameter Δ(k) is assumed to vary only with the angle θ between the direction k^ of the quasiparticle wave vector and the c axis of the crystal (chosen to be the z direction). We employ a formulation for calculating the linear conductivity in which the collision frequency is directly related to the imaginary part of the single-particle self-energy resulting from various elastic and inelastic collisions. In the presence of gap anisotropy, there is finite absorption below the in-plane gap 2Δ ab , assumed to be the maximum energy gap. We find that with a bilevel gap parameter consisting of an in-plane value Δ ab , a c-axis value of about ¼ to 1/3 of Δ ab , and a sharp transition between them at ||cosθ||~0.5, we are able to fit quite well the experimental infrared absorption data for the single crsytal YBa 2 Cu 3 O 7 , in which q is along the c axis. With hQ ab and ω c , the observed data in the region ω ab /h can be fitted even with a low normal-state collision frequency derived from the normal-state dc conductivity. However, we find that to get a good fit in the region beyond ω=2Δ ab /h, ω c must necessarily be large and close to 2.5Δ ab /h. Whether this type of frequency-dependent ω c implies electron-electron collision effects in the normal state beyond the normal Fermi-liquid picture or wether this is merely due to the existence of another inelastic scattering channel in the system with a low threshold, cannot be resolved unambiguously.

A generalized Gorkov formalism of superconductivity in a layered system with non-primitive lattice structure is given. This is used to justify theoretically a model of highT c oxide superconductors proposed recently by one of us (SSJ). A numerical estimation of the critical temperature as a function of the number of superconducting layers is mentioned.

A generalized pairing theory of superconductivity in layered crystals is formulated in terms of an arbitrary dynamical interaction, V(r1r2; t1−t2), among the electrons. This has been done within the framework of the Gorkov mean field theory, with the introduction of an appropriate set of states to represent the single particle motion in the layered crystals. The layer representation is band-like in the plane of the layers and localized in the perpendicular direction. This enables us to derive the equation for the superconducting state which includes intra-and inter-layer polarization interactions involving exchange of all possible electronic and ionic excitations in the system within the strong coupling formalism. An equation for the critical temperature Tc of the system has been obtained by solving the linearized gap equation in terms of a suitably averaged dynamical interaction. We specify from first principles the various approximations required to obtain the simpler forms of the Tc-equation used in the literature for investigating its dependence on the structure and number of conducting layers in the new high-Tc systems. In general, we find that the dynamical interactions can involve a maximum of any four different layers with intra- and inter-layer pairings. In the extreme layer approximation, where the excitations are highly localized to within individual layers, the interaction connects only a maximum of any two layers. These considerations still imply that the required attractive interaction for intra-layer Cooper pairing in a conducting layer may arise from both intra- and inter-layer couplings and possible exchange of excitations in the neighboring layers whether conducting or insulating.

The nature of electronic Raman scattering from anisotropic layered high- T c materials has been considered. Approximate expressions for the electronic Raman scattering from both charge-density fluctuations (CDF) and spin-density fluctuations (SDF) in these materials with nonparabolic energy bands and anisotropic Fermi surfaces have been derived. It is shown that in the normal state the unscreened part of the single-particle electronic Raman scattering has a width of about 2ω cn in the collision-dominated regime in which the normal state collision frequency ω cn ⪢ q · v f , where ħ q is the momentum transfer in the scattering process and v F is the Fermi velocity. Although, the normal state Raman spectrum is not as flat as observed experimentally, the possibility that most of the spectrum may be arising from such collision-dominated single-particle excitations, cannot be ruled out completely. More careful experimentation is required to confirm unambiguously the existence of any novel type of electronic excitations in the system.

New oxide superconductors with layered structure are expected to have anisotropic energy gap in the generalized BCS pairing theory. The gap parameter $$2\Delta (\hat k)$$ can be quite different for $$\hat k$$ perpendicular to the plane of the layers as compared tok parallel to layer planes. Because of short coherence lengths ξ, quite small compared to the normal state carrier meanfree pathl, the effect of these anisotropies do not average out, as in many of the conventional superconductors. For a proper comparison of experimental results with the correct predictions of the pairing theory, a formulation is developed to obtain important physical quantities like specific heat and infrared absorption in the superconducting state of such anisotropic systems. This includes a brief account of the pairing theory generalized to layered crystals with arbitrary number of layers per unit cell, not necessarily equidistant. In an explicit model for the anisotropy of the gap parameter ink-space, with a simple form for the nonspherical Fermi-surface, it is shown that the low-temperature specific heat can have even a linear or a power-law temperature-dependence in the superconducting state. Even if the gap parameter does not vanish anywhere, its smeared-out exponential temperature-dependence may be difficult to be distinguished experimentally from a power-law behaviour. Similarly, it is shown that in the case of appreciable anisotropy, infrared absorption can take place much below the in-plane gap parameter $$2\Delta _t (\hat k_t )$$ , wherek t is the wavevector in the plane of the layers.

We use different types of determinantal Hartree-Fock (HF) wave functions to calculate variational bounds for the ground state energy of spin-half fermions in volume V_0, with mass m, electric charge zero, and magnetic moment mu, which are interacting through long range magnetic dipole-dipole interaction. We find that at high densities when the average inter particle distance r_0 becomes small compared to the magnetic length r_m, a ferromagnetic state with spheroidal occupation function, involving quadrupolar deformation, gives a lower energy compared to the variational energy for the uniform paramagnetic state. This HF variational bound to the ground state energy turns out to have a lower energy than our earlier calculation in which instead of a determinantal wavefunction we had used a positive semi-definite single particle density matrix operator whose eigenvalues, having quadrupolar deformation, were allowed to take any value from 0 to 1. This system is of course still unstable towards infinite density collapse, but we show here explicitly that a suitable short range repulsive (hard core) interaction of strength U_0 and range a can stop this collapse.The existence of a stable high density ferromagnetic state with spheroidal occupation function is possible as long as the ratio of hard-core and magnetic dipole coupling constants is not very small compared to 1., Comment: A shorter version of this paper will appear in Pramana - Journal of Physics

We obtain the best upper bound for the ground-state energy of a system of chargeless fermions of mass $m$, spin $s=1∕2$, and magnetic moment $\ensuremath{\mu}\stackrel{P\vec}{s}$ as a function of its density in the fully spin-polarized Hartree-Fock determinantal state, specified by a prolate spheroidal plane-wave single-particle occupation function ${n}_{\ensuremath{\uparrow}}(\stackrel{P\vec}{k})$, by minimizing the total energy $E$ at each density with respect to the variational spheroidal deformation parameter ${\ensuremath{\beta}}_{2},0\ensuremath{\leqslant}{\ensuremath{\beta}}_{2}\ensuremath{\leqslant}1$. We find that at high densities, this spheroidal ferromagnetic state is the most likely ground state of the system, but it is still unstable towards the infinite-density collapse. This optimized ferromagnetic state is shown to be a stable ground state of the dipolar system at high densities, if one has an additional repulsive short-range hardcore interaction of sufficient strength and nonvanishing range.

Energy levels, radiative rates, and lifetimes are calculated for all levels of 3s23p, 3s23d, 3s3p2, 3s3d2, 3s3p3d, 3p23d, 3s3d2, 3p3d2, 3p3, and 3d3 configurations of Al-like tungsten ion (W XLVII). Multiconfigurational Dirac–Fock (MCDF) method is adopted for calculating energy levels and radiative rates. Oscillator strengths, radiative rates, and line strengths are reported for some E1 transitions from the ground level. Comparisons are made with the available data in the literature and good agreement has been found which confirms the reliability of our results.