Radial Coupling Research Articles

Double window configuration as a low cost microwave waveguide window for plasma applications

Waveguide windows are major components of a transmission line used in microwave plasma devices. The function of the waveguide window is to provide vacuum isolation of the source side from the plasma chamber while transmitting microwaves with minimum attenuation. Commonly a single thin dielectric plate is sandwiched between a choke type flange and a flat flange and is used as a waveguide window. To arrive at a better window configuration in terms of the low power reflection coefficient, the voltage standing wave ratio calculation is carried out for different window configurations (single window and double window) and for various window thicknesses. It is found that the power reflection is the minimum in the case of double window configuration. The minimum power reflection is as low as 0.8% for a combination of alumina and a quartz plate each of 1 cm thickness in the double window configuration. Also, it is more advantageous to use radial microwave coupling than axial coupling in order to increase the life time of the microwave waveguide window.

Coupled-channel calculations of excited-atom collisions

Recent calculations of excited-atom collisions based on the coupled-channel formalism are reviewed. Such calculations of electronic excitationprocesses require additional information (such as radial coupling matrix elements) beyond the adiabatic potential surfaces normally provided by ab - initio electronic structure calculations. Several examples are discussed that illustrate various strategies for obtaining this additional information. The first example involves collisions of heavy atoms, particularly xenon. In this case, the inner-shell electrons exhibit relativistic effects, and the effects of the spin-orbit operator can be quite large. In addition, the open-shell core has non-zero spin and orbital angular momentum. For these collisions the inner-shell electrons are treated using effective core potentials, and a model Hamiltonian is developed to handle the large spin-orbit effects and the open-shell core. The second example involves collisions in which the target atoms are spatially aligned. These calculations required radial coupling terms as well as the determination of explicit state-to-state cross-sections between specific angular momentum states. These examples demonstrate that collisions of a high level of complexity can now be quantitatively treated.

Effect of poling process on the piezoelectric and dielectric properties of Nb and Sr-doped PZT ceramics

The piezoelectric and dielectric properties of Sr and Nb doped lead zirconate titante (PZT) used for electroacoustic transducers have been investigated as a function of the poling field and poling time. The optimum poling conditions were determined from the measurement of maxima of the radial planar coupling factor (kp) and the relative dielectric constant (εr) at various poling parameters. The data showed that the mentioned quantities reach the maximum values and then saturate at an external electric field up to the saturation field in a suitable time. Large external fields associated with the extension of poling time above the optimal values produced the degradation of investigated electromechanical coefficient and the dielectric constant.

State- and isotope-dependent charge transfer of with atomic hydrogen in astrophysical and fusion plasmas

State- and target-isotope-dependent cross sections for electron capture in collisions of with , , and are presented for the energy range 0.01 - . Results are given for capture via radial coupling into the , , , , , , and states and are obtained through a close-coupled, quantum-mechanical, molecular-orbital method. Fully ab initio molecular data determined with the spin-coupled valence-bond method are incorporated. Rate coefficients for temperatures between 1000 and K are also presented. Applications to astrophysical environments and laboratory plasmas are addressed. The importance of state-dependent parameters for the modelling of nebulae emission lines and for fusion plasma impurity diagnostics and the potential significance of isotope effects to models of the edge region of a tokamak device are briefly discussed.

Ab initio study of charge transfer in low-energy collisions ofSi4+with helium

We present state-dependent and total charge transfer cross sections for the process ${\mathrm{Si}}^{4+}$(${2\mathrm{p}}^{6}$)+He(${1\mathrm{s}}^{2}$)\ensuremath{\rightarrow}${\mathrm{Si}}^{3+}$(3l)+${\mathrm{He}}^{+}$(1s), where l=s,p, in the collision energy range 0.004--10 eV/amu. The cross sections are determined using a close-coupled quantal method. Fully ab initio adiabatic potentials and nonadiabatic radial coupling matrix elements obtained with the spin-coupled valence-bond method are incorporated. Rate coefficients for temperatures between 1000 and 50 000 K and results for isotopic $^{3}\mathrm{He}$ are also presented. Astrophysical applications are briefly discussed.

Extent of radial sarcomere coupling revealed in passively stretched cardiac myocytes.

The complex geometry of the heart leads to a time-varying and nonuniform distribution of stress and strain on the myocardium during the cardiac cycle. This study investigated the sarcomere length and striation registration behavior resulting from a gradient of strain imposed on the cytoskeleton of isolated cardiac myocytes. Within a myocyte, sarcomeres are organized into domains separated by strips of mitochondria and nuclei. Sarcomeres are interconnected radially at the Z-disc by the exosarcomeric cytoskeleton, composed primarily of the intermediate filament desmin. Chemically skinned myocytes isolated from adult rat hearts were attached using to concentric double-barreled pipettes in such a way as to induce a gradient of applied strain across the width of the cell. At rest lengths, there was variation in the sarcomere length between domains of attached cells. Upon stretch, most domains exhibited proportional increases in sarcomere length, with the initial differences being maintained. However, some domains did not behave in synchrony with the others at shorter sarcomere lengths. Thus, the coupling between sarcomeric domains can allow for a non-linear relationship between sarcomere length and strain. Sarcomeres were tightly coupled in the radial direction within a single domain, but striation mis-registration of up to 0.20 micron between domains was induced by stretch. This indicates the looser nature of the cytoskeletal coupling between domains compared to that within domains. Thus, cardiac myocytes are not rigid functional units, but composite structures whose components consist of functionally semi-independent domains tethered by the cytoskeletal intermediate filament lattice.

Measurement of Autoionizing Electrons from the Na(2p53s2)2P State in Slow Na+-He Collisions

Ejected electron spectra from the autoionizing state in Na + –He collisions have been measured with incident Na + ion energies from 1 keV to 2.25 keV. The anisotropy parameter β 2 for electron ejection from the autoionizing state Na(2p 5 3s 2 ) 2 P is presented. The alignment of the autoionizing state is discussed in relation to the energy dependences of the anisotropy parameter β 2 . The energy dependence of the anisotropy parameter β 2 is interpreted as being due to an excitation by a radial coupling between two ∑ states, followed by a full rotation of the quasimolecule during the slow Na + –He collisions.

The radial magnetic coupling studies of perpendicular magnetic gears

The torque of the radial magnetic coupling between perpendicular magnetic gears with different magnetic poles has been investigated experimentally. The torque of magnetic coupling decreases with increasing the distance between the magnetic gears. For different multipole magnetic couplings with the same magnetic field strength, the torque of magnetic coupling increases as the number of magnetic poles increases for distances smaller than a critical separation distance d/sub c/, but it is reversed as the separation distance becomes larger. This critical separation distance for our sintered NdFeB magnet system with an iron yoke of 2 mm thickness is roughly between 9 and 11 mm. This phenomenon is explained by analyzing the magnetic coupling strength of different poles of magnets on the perpendicular magnetic gears.

Effects of an avoided crossing on linewidths of resonances in the H2 i3Π g state

We have investigated the influence of nonadiabatic effects on the linewidths of quasi-bound rovibrational levels in the i3Πg state of molecular hydrogen. This state has a potential barrier due to the interaction of then=33Πg Rydberg series and the Q13Πg valence state. The radial coupling with the higher lying3Πg states has been modelled into a diabatic problem. The widths of thev=4 and 5 levels, a measure for their lifetimes, have been determined both in the adiabatic i3Πg potential, and in the two-state system. The results show small shifts of the i3Πg (v′=4,5;N′=1) levels of a few wavenumbers, and a significant increase of 49% in the lifetimes of these levels. Both effects are large enough to be important in spectroscopic experiments. The magnitude of the effect is in accordance with observed linewidths obtained in recent experiments. Model calculations for differently shaped potential barriers have been carried out to study the generality of the above conclusions.

HSTERM — A program to calculate potential curves and radial matrix elements for two-electron systems within the hyperspherical adiabatic approach

A FORTRAN 77 program is presented which calculates potential curves and matrix elements of radial coupling for two-electron systems using the hyperspherical coordinate method. The adiabatic and diabatic-by-sector close-coupling approaches are considered. The program calculates also the overlap matrices on borders of all sectors which are necessary for integration of close-coupling hyperradial equations within the sector-diabatic approach. It performs also the computation of the angular part of dipole amplitudes (in the length and acceleration forms) for dipole transitions between two given atomic states. The convergence and accuracy of the computational scheme elaborated are studied in details. Radial matrix elements computed by the HSTERM program can be used for the solution of the bound state and scattering problems for two-electron systems in both the adiabatic and diabatic-by-sector close-coupling approaches.

Electric Properties of Pb(Sb1/2Nb1/2)O3-PbTiO3-PbZrO3 Ceramics Modified with Certain Additives

Effects of additives on the ceramic and electric properties of Pb(Sb1/2Nb1/2)O3-PbTiO3-PbZrO3 ceramics in a perovskite-type structure were investigated. Addition of small amounts of MnO2 or NiO increased the sintered density. However, larger amounts of MnO2 or NiO lowered the sintered density. Small amounts of MnO2 or NiO promoted the grain growth of the ternary base composition. The microstructure indicated that small amounts of MnO2 produced a fine, uniform grain structure and addition of NiO produced clearer grain boundaries and larger grain size than MnO2 addition. The resistivity, dielectric and piezoelectric properties of the base composition were improved markedly through selection of additives in proper amounts. High mechanical quality factor, Q M (2070), low dielectric dissipation factors (36×10-4) and high radial coupling coefficient, k p (54%) were obtained by addition of MnO2.

Numerical treatment of inelastic He++Ne collisions at low energy

We report numerical results for the differential cross sections for different inelastic channels of the He++Ne collision system. The collision energies range from 100eV to 200eV. The potentials and the nonadiabatic interactions are described by a realistic model based on quantum chemical data. Radial and rotational coupling are included, as well as the spin-orbit interaction. A quantum-mechanical description of the heavy-particle motion is used. The results mostly show a good agreement with the experiment, finer details such as the spin-inversion probability of the He+ ion are reproduced less satisfactorily.

Potential curves and nonadiabatic matrix elements for collisions involving fragments of the HeN+ molecular ion

Ab initio multireference CI calculations have been carried out for the HeN+ molecular ion in order to describe collision processes between its constituent neutral and ionized atoms. The accuracy of these calculations is evaluated by means of a comparison of results obtained at large internuclear separations with the corresponding asymptotic energies deduced from atomic spectral data. Energy values are computed for the eleven lowest He++N and He+N+ atomic limits and average discrepancies relative to the experimental excitation energies up to 110 000 cm−1 are found to lie in the 1000–3000 cm−1 range, of which only 200 cm−1 appears to be the fault of the configuration interaction (CI) technique itself, with the main portion of the error stemming from the choice of atomic orbital (AO) basis instead. The HeN+ X 3Σ− ground state is calculated to have a De value of only 1414 cm−1, but the excited 2 3Π state has a much larger value of 22 133 cm−1 by virtue of an avoided crossing with the lower state of this symmetry. The corresponding radial nonadiabatic coupling is responsible for a large cross section for an excitation process between the N+(3Pg)+He and N+(3Du)+He channels which indirectly provides an efficient electron-capture mechanism leading to the N(4Su)+He+ exit channel. Additional nonadiabatic matrix elements for rotational and spin–orbit coupling have also been obtained and analyzed, as well as transition moments between the various HeN+ molecular states calculated.

Wiener reconstruction of density, velocity and potential fields from all-sky galaxy redshift surveys

We present a new method for recovering the cosmological density, velocity, and potential fields from all-sky redshift catalogues. The method is based on an expansion of the fields in orthogonal radial (Bessel) and angular (spherical harmonic) functions. In this coordinate system, peculiar velocities introduce a coupling of the radial harmonics describing the density field in redshift space but leave the angular modes unaffected. In the harmonic transform space, this radial coupling is described by a distortion matrix which can be computed analytically within the context of linear theory; the redshift space harmonics can then be converted to their real space values by inversion of this matrix. Statistical noise is mitigated by regularizing the matrix inversion with a Wiener filter. The method yields a minimum variance estimate of the density field in real space. In this coordinate system, the minimum variance harmonics of the peculiar velocity and potential fields are related to those of the density field by simple linear transformations. Tests of the method with simulations of a CDM universe and comparison with previously proposed methods demonstrate it to be a very promising new reconstruction method for the local density and velocity field. A first application to the 1.2 Jy IRAS redshift survey is presented.

Analysis of rotational coupling in collisions of Li+ with Ne leading to double excitation of Ne

Electron angular distributions due to autoionization of Ne, doubly excited to the (2p43s2)1D state in collisions with Li+ in the energy range 1.2-2.2 keV, are measured in coincidence with Li+ scattered into a well defined direction ( Phi =0 degrees , Theta cm=10.8 degrees ). The experimental findings are analysed with the help of a collision model proposed earlier. In this model the initial excitation occurs by radial diabatic coupling to a molecular Sigma -state at small distances, followed by rotational coupling to Pi - and Delta -states at intermediate distances in the second half of the collision. The energy splitting between the Sigma -, Pi - and Delta -states is described by a model function. By adapting two parameters of this model function, the experimental findings can be reproduced within the experimental error in numerical calculations involving the relevant set of coupled differential equations.

The radial magnetic coupling studies between magnetic gears

The torque of the radial magnetic coupling between magnetic gears with different magnetic poles has been investigated by experimental and computer simulation analyses. The torque of magnetic coupling is sensitive to the number of magnetic poles, and it decreases with increasing the distance between the magnetic gears. We can increase the torque by increasing the number of poles for magnetic coupling between magnetic gears with short separation distance. The three dimensional computer simulation calculated values of the torque of magnetic coupling by both the virtual work technique and Maxwell stress tensor method are in excellent agreement with the experimentally measured values.

リチウムニオブ酸鉛‐チタン酸鉛‐ジルコン酸鉛系磁器の相転移と電気的性質

Solid solution ceramics in the system xPb(Li1/4Nb3/4)O3-yPbTiO3-zPbZrO3 were prepared by the solid state reaction of powder materials. The ceramic, dielectric, and piezoelectric properties and crystal structures of the products were studied. The compositions within the ternary system were sintered much more easily than the end compositions, and a well sintered high density ceramics was obtained for the compositions near the morphotropic transformation. Piezoelectric ceramics with high relative dielectric constants, high radial coupling coefficient and low resonant resistance were obtained for the composition near the morphotropic transformation. The composition Pb(Li1/4Nb3/4)0.2Ti0.4Zr0.4O3 showed the highest radial coupling coefficient.

Electric Properties of Pb(Sb1/2Nb1/2)O3–PbTiO3–PbZrO3 Ceramics

Solid-solution ceramics of ternary system xPb(Sb1/2Nb1/2)O3– yPbTiO3– zPbZrO3 were prepared by the solid-state reaction of powder materials. Ceramic, electric, dielectric and piezoelectric properties and crystal structures of the system were studied. Sintering of the system xPb(Sb1/2Nb1/2)O3– yPbTiO3– zPbZrO3 is much easier than that of each end composition, and well-sintered high-density ceramics were obtained for the compositions near the morphotropic transformation. Piezoelectric ceramics with high relative dielectric constants, high radial coupling coefficient and low resonant resistance were obtained for the composition near the morphotropic transformation. The composition Pb(Sb1/2Nb1/2)0.075Ti0.45Zr0.475O3 showed the highest dielectric constant (εr=1690), and the composition Pb(Sb1/2Nb1/2)0.05Ti0.45Zr0.5O3 showed the highest radial coupling coefficient (kp=64%).

Electron capture by state-selected O2+ ions from atomic hydrogen

Ab initio methods are used to obtain the adiabatic potential energies and the corresponding non-adiabatic radial and rotational coupling matrix elements for all of the doublet and quartet Sigma , Pi and A states of OH2+ which contribute to electron capture by state-selected O2+ from atomic H. Semiclassical methods are used to treat the collision dynamics. Results are presented both for ground (3P) and metastable (1D,1S) state ions in the range of collision energies from 20 eV to 30 keV. The cross sections for electron capture by ground state ions are about a factor of three larger than for metastable ions over a very wide energy range. The effect of rotational mixing of the 4 Sigma - and 4 Pi states in the entry channel for ground state ions is found to be large at energies in excess of a few 100 eV. The results are in excellent agreement with the experimental energy gain spectra.

Asymptotic theory of s-->p charge exchange: Extended Demkov model.

The asymptotic theory is developed for the calculation of the charge-exchange amplitudes for large impact parameters \ensuremath{\rho}. The case of the small energy defect is considered which corresponds to the Demkov model (nonadiabatic transitions induced by the switching of the wave functions from the atomic states to the molecular-orbital regime). The effect of electron momentum transfer is included. The initial and final states with nonzero orbital momentum are considered with a special emphasis on the simplest case of s\ensuremath{\rightarrow}p charge exchange. The large-\ensuremath{\rho} asymptote of the charge-exchange amplitude is calculated both for the transitions induced by radial and rotational couplings. One-center depolarization transitions (changing the projection of the angular momentum) are also incorporated in the general theory. The orientation and alignment parameters characterizing the asymmetry created in the s\ensuremath{\rightarrow}p process are obtained in a simple analytical form for large \ensuremath{\rho} (or small scattering angles). They include contributions both from the one-center depolarization and from the competition of the charge exchange induced by radial and rotational coupling. The relative role of both mechanisms is analyzed and a strong dependence of the asymmetry parameters on the sign of the process energy defect is predicted. The theory is applied to the process Na(3p)+${\mathrm{H}}^{+}$\ensuremath{\rightarrow}${\mathrm{Na}}^{+}$+H(n=2).