Resonant alteration of propagation in guiding structures with complex Robin parameter and its magnetic-field-induced restoration

Solutions of the scalar Helmholtz wave equation are derived for the analysis of the transport and thermodynamic properties of the two-dimensional disk and three-dimensional infinitely long straight wire in the external uniform longitudinal magnetic field B under the assumption that the Robin boundary condition contains extrapolation length Λ with nonzero imaginary part Λ_i. As a result of this complexity, the self-adjointness of the Hamiltonian is lost, its eigenvalues E become complex too and the discrete bound states of the disk characteristic for the real Λ turn into the corresponding quasibound states with their lifetime defined by the eigenenergies imaginary parts E_i. Accordingly, the longitudinal flux undergoes an alteration as it flows along the wire with its attenuation/amplification being E_i-dependent too. It is shown that, for zero magnetic field, the component E_i as a function of the Robin imaginary part exhibits a pronounced sharp extremum with its magnitude being the largest for the zero real part Λ_r of the extrapolation length. Increasing magnitude of Λ_r quenches the E_i − Λ_i resonance and at very large Λ_r the eigenenergies E approach the asymptotic real values independent of Λ_i. The extremum is also wiped out by the magnetic field when, for the large B, the energies tend to the Landau levels. Mathematical and physical interpretations of the obtained results are provided; in particular, it is shown that the finite lifetime of the disk quasibound states stems from the Λ_i-induced currents flowing through the sample boundary. Possible experimental tests of the calculated effect are discussed; namely, it is argued that it can be observed in superconductors by applying to them the external electric field E normal to the surface.     

Presheath in Fully Ionized Collisional Plasma in a Magnetic Field

The quasineutral presheath layer at the boundary of fully ionized, collisional, and magnetized plasma with an ambipolar flow to an adjacent absorbing wall was analyzed using a two fluid magneto‐hydrodynamic model. The plasma is magnetized by a uniform magnetic field B , imposed parallel to the wall. The analysis did not assume that the dependence of the particle density on the electric potential in the presheath is according to the Boltzmann equilibrium, and the dependence of the mean collision time τ on the varying plasma density within the presheath was not neglected. Based on the model equations, algebraic expressions were derived for the dependence of the plasma density, electron and ion velocities, and the electrostatic potential on the position within the presheath. The solutions of the model equations depended on two parameters: Hall parameter (β ), and the ratio (γ ), where γ = ZT_e /(ZT_e + T_i ), and T_e , T_i and Z are the electron and ion temperatures and ionicity, respectively. The characteristic scale of the presheath extension is several times r_i /β , where r_i is the ion radius at the ion sound velocity. The electric potential could have a non monotonic distribution in the presheath. The ions are accelerated to the Bohm velocity (sound velocity) in the presheath mainly near the presheath‐sheath boundary, in a layer of thickness ～r_i /β . The electric field accelerates the ions in the whole presheath if their velocity in the wall direction exceeds their thermal velocity. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Proton shielding function for hydrogen chloride

For a diatomic molecule the nuclear shielding constant σ(ξ) of either nucleus can be expanded as a power series in the relative displacement from equilibrium ξ. Thus the nuclear shielding function is

where ξ=(r-r _e)/r _e with r the actual bond length and r _e the equilibrium bond length. The σ_e ⁽ⁱ⁾ are molecular parameters. By experimental observation of the temperature dependence of the proton magnetic shielding of hydrogen chloride gas it is possible, after allowing for intermolecular effects, to obtain the values σ_e ⁽⁰⁾=32·48 (±0·33) p.p.m. and σ_e ⁽¹⁾=-100 (±24) p.p.m. for the coefficients of the proton shielding function. Using this data it is possible to show that the isotope shift between H³⁷Cl and H³⁵Cl is about 0·001 p.p.m. By a comparison with earlier results for molecular hydrogen it would appear that in some instances differences in vibrational and rotational averaging may alter chemical shifts between different compounds by amounts considerably larger than the experimental error in chemical shift measurement.     

Collective Dust‐Dust Attraction in Strong Magnetic Field

It is shown that the collective dust‐dust attraction is enhanced by strong magnetic fields larger then the critical magnetic field determined be the condition that the Lorentz force acting on ions is larger than the friction of ions on dust grains related with the dust drag. It is demonstrated that with an increase of the magnetic field the deepness of the attraction potential well is increased in all directions to the magnetic field, that the distance of the minimum of the potential well along the magnetic filed (in both directions) is changed only slightly while the distance of the minimum of the attraction potential well is substantially decreased for directions perpendicular to the magnetic field. This means that the structures formed by attraction forces such as plasma crystals will be compressed perpendicular to the magnetic field (inter‐dust distance becomes smaller) and that the melting transition temperature should increased with an increase of the strength of the magnetic field. Numerical results are presented for dependence of the attraction potential well on the ratio of the strength of the magnetic field to the critical magnetic field strength, on the parameter P = n_dZ_d/n_i (n_d and n_i being the dust and ion densities respectively) and on the temperature ratio τ = T_i/T_e (T_e and T_i being the electron and ion temperatures respectively). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

An anharmonic force field for carbonyl sulphide

A 16-parameter force field for OCS based on curvilinear coordinates is presented in table 2 and the agreement between observed and calculated transitions and rotational constants is indicated in tables 4, 5 and 6. The computational approach differs from that of Morino and Nakagawa [2] and similar work on other molecules by other authors, in that perturbation theory is eschewed and the calculated vibrational transitions and rotational constants are derived via the numerical solution of a large matrix. The usual parameters x_ij , y_ijk , α _i ^B and γ _ij ^B are thereby rendered inappropriate intermediates. The approach also leads to estimates of B _e - B ₀ for each isotopic species and thence suggests equilibrium distances r _CO = 1·155386(21) Å and r _CS = 1·562021(17) Å.     

关于等离子体中的瞬变过程

利用Spitzer的广义欧姆定律分析等离子体中由垂直于磁场的压强梯度所引起的宏观瞬变性质。在垂直于磁场方向的初始流动速度为零的条件下,得出在恒稳磁场中的瞬时扩散系数(当ω_ceτ?1)为 D= (2km_ec²)/e² T/(B²τ)+(kc)/eT/Be^-m_e/(miτ)tsinω_cit,式中τ为电子离子的平均碰撞时间间隔。     

On Island Formation in a Locally Perturbed Tokamak Equilibrium

To control the plasma transport at the edge of a tokamak the outer flux surfaces can be artificially destroyed by applying a resonant helical magnetic field, as it is demonstrated at Pulsator [1],[2], [3], Tore Supra [4],[5] and proposed for TEXTOR-94 [6] in the concept of “ergodic divertors”. As a measure of the efficiency of the perturbation field e.g. the level of the field line diffusion coefficient DFL the width Δ_i of the magnetic islands and the related Chirikov parameter are of importance [7],[8],[9],[10]. For the planned Dynamic Ergodic Divertor (DED) at TEXTOR-94 where the perturbation coils are located at the high field side the standard expression for Δ_i using the Fourier components of the magnetic field perturbation [7] leads to results significantly different from field line tracing calculations [11]. The standard expression is commonly used in terms of the perturbation magnetic field δB [5],[7],[8],[9],[12],[13]. But when replacing the Fourier components of the perturbation vector potential by those of the magnetic field finite aspect ratio effects have been neglected so far. For present tokamaks with ? = r/R ? 0.3 this can lead to an error in the field line diffusion of one to two orders of magnitude. In this paper it is shown that taking into account the finite aspect ratio at this point leads to correct results compared to the highly precise field line tracing calculations by the Gourdon code. The island width then is recognized to depend significantly on the poloidal position of the perturbation field. This is in contrast to the standard expression. Also the role of the choice of the magnetic coordinate system is considered.     

A test of the rm method of structure determination

The r_m method of determining molecular structures from isotopic zero-point rotational constants is tested by applying it to synthetic data for OCS calculated from an assumed equilibrium structure and force field. The results show that the r_m structure is significantly different from the r_e structure, unless the substitution coordinates used in the r_m calculation are corrected for the use of finite changes of mass Δm_i by extrapolation to Δm_i = 0. The latter procedure is not usually feasible experimentally. In the ordinary r_m method the errors are generally comparable in magnitude to those in Costain's r_g method. An exception arises when the number of structural parameters equals the number of independent moments of inertia of a single isotope (e.g., a diatomic molecule or a symmetrical XY₂ molecule), in which case the r_m structure is in good agreement wich the r_e structure.     

Rotational properties of annulus dusty plasma in a strong magnetic field

The collective dynamics of an annulus dusty plasma formed between a co-centric conducting (non-conducting) disk and ring configuration is studied in a strongly magnetized radiofrequency (rf) discharge. A superconducting electromagnet is used to introduce a homogeneous magnetic field to the dusty plasma medium. In the absence of the magnetic field, the dust grains exhibit thermal motion around their equilibrium position. The dust grains start to rotate in the anticlockwise direction with increasing magnetic field (B > 0.02 T ), and the constant value of the angular frequency at various strengths of the magnetic field confirms the rigid body rotation. The angular frequency of dust grains linearly increases up to a threshold magnetic field (B > 0.6 T ) and after that its value remains nearly constant in a certain range of magnetic field. Further increase in magnetic field (B > 1 T ) lowers the angular frequency. Low value of the angular frequency is expected by reducing the width of the annulus dusty plasma or the input rf power. The azimuthal ion drag force due to the magnetic field is assumed to be the energy source which drives the rotational motion. The resultant radial electric field in the presence of a magnetic field determines the direction of rotation. The variation of floating (plasma) potential across the annular region at given magnetic field explains the rotational properties of the annulus dusty plasma in the presence of a magnetic field.     

Kinetic analysis of the ionization ratio effects on a three‐species plasma

In partially ionized plasmas, the energy transferred to electrically charged species by the electromagnetic field can be partly channelized to the population of neutrals, due to interspecies collisional processes. Depending on the relative density of neutrals, these effects may govern the collective plasma dynamics by drastically modifying particle dynamics and energy‐transport processes with respect to the fully ionized plasma‐approximation models. In this work, the influence of the ionization ratio r_i on a partially ionized plasma is analysed by means of a three‐species one‐dimensional kinetic model to compute transient and steady state velocity‐dependent distribution functions. The conservative collision operators accounting for charge–charge and charge–neutral interactions allow studying several plasma scenarios with the same entire number of particles per unit of volume but for an increasing r_i parameter, in the presence of a modulated signal‐like electric field. For a sequence of plasma scenarios of fixed r_i, ranging from typical weakly ionized to highly ionized plasma values r_i ～ 10^?7–10^?4, the mass species flows are examined. These flows behave linearly with respect to r_i up to a value r_i ? 10^?5 from which the quasi‐linear dependence is critically altered. The convection–diffusion equations are solved with the semianalytical Propagator Integral Method, which behaves well to deal with conservative operators, density, and field discontinuities, allowing for the use of collision terms of disparate time and spatial characteristic scales. The results can be relevant to a wide class of plasma systems and to analyse the ionization ratio effects on transport coefficients.     

Ab initio calculations for propyne and the hydrogen bonded complex NH H C C CH 3 3

The hydrogen-bonded cluster NH₃ …H—C≡C—CH₃ has been investigated by means of the coupled electron pair approximation, making use of a basis set of 198 contracted Gaussian-type orbitals. The calculated equilibrium structure is r _1^e (N—H) = 1?0127 Å, α_e(∠HN…H) = 112?32°, R _1^e (N…H) = 2?3593 Å, r _2^e (acetylenic C—H) = 1?0690 Å, R _2^e (C≡C) = 1?2078 Å, R _3^e (C—C) = 1?4711 Å, r _3^e (C—H) = 1?0894 Å and β_e(∠CCH) = 110?50°. The recommended equilibrium dissociation energy is D _e = 12?4±0?5 kJ mol^-1 and the calculated equilibrium dipole moment is μ_e = – 1?468 D, with the positive end of the dipole at the ammonia protons. Harmonic wavenumbers and absolute infrared intensities for the totally symmetric modes are calculated. Compared with free propyne the acetylenic CH stretching vibration experiences a bathochromic shift of 93 cm^-1 and an intensity enhancement by a factor of 5?5.     

Mössbauer analysis and magnetic properties of Invar Fe–Ni–C and Fe–Ni–Mn–C alloys

The saturation magnetization and the hyperfine magnetic field of different f.c.c. Fe–Ni based alloys containing nearby 29 at .% Ni were studied as a function of temperature and for different Carbon and Manganese contents. We have observed abnormal behaviors that are explained in terms of mixed exchange interactions between atomic spins: J _NiNi(r _i ) < 0, J _FeFe(r _i ) > 0, J _NiFe(r _i ) < 0.     

The millimeterwave spectrum of germyl fluoride: Determination and comparison of the effective, substitution, and equilibrium structures

The ground state rotational spectrum of germyl fluoride was measured up to 1273 GHz (J ≤ 63). The rotational constants and quartic and sextic centrifugal distortion constants have been determined accurately for five isotopic species in natural abundance (^{70/72/73/74/76}Ge). The high accuracy of the rotational constants of these five isotopomers allowed us to study the mass dependence of the substitution coordinate of Ge. Equilibrium rotational constants of ⁷⁴GeH₃F were deduced with the help of the axial rotational constant and the rotation-vibration interaction constants determined by high resolution infrared spectroscopy. The r₀, r_,I, and r_e structures of GeH₃F were determined.     

Observation of the fast component in the fluorescence of gaseous SO2 excited to the A1A2 state in the presence of a magnetic field

Effects of an external magnetic field (B) on the SO₂ fluorescence have been examined under excitation of the ‘C’ band and the single rotational levels of the ‘B’ and ‘E’ bands of the A(¹A₂) ← X¹A₁ transition. For the ‘C’ band, the total SO₂ fluorescence was studied, while for excitation of the single rotational levels, fluorescence of the single rotational lines of (^rR₅(5) (31711 cm^-1), ^pP₇(7) (31662 cm^-1)) (‘E’ band) and of (^rR₈(8) (31000 cm^-1), ^pP₁₀(10) (30927 cm^-1)) (‘B’ band) was studied. Decay of the SO² fluorescence was studied with nanosecond time resolution in the 1?5–50 mTorr region. In the presence of a magnetic field, decay of the total SO₂ fluorescence and of the fluorescence belonging to the single rotational lines were fitted by the bi-exponential functions. In the case of the total SO₂ fluorescence, this function also includes the time independent term, which, however, is dependent on a magnetic field. The time independent term belongs to the long-living component, which can be approximated by a constant in the time-scale studied. Radiationless processes induced by an external field were directly observed. The magnetic field and pressure dependences of the processes induced by a field were studied under excitation of the SO₂ fluorescence by light of a different wavelength. The data obtained were explained by the direct mechanism.     

Dispersion of electromagnetic waves in the presence of magnetic monopoles of electron mass in a uniform magnetic field

The dispersion relation of electromagnetic waves in the presence of magnetic monopoles of electron mass in a uniform magnetic field is obtained. The waves of the frequencyω in the range ω_ϱi<Ω_i<ω<Ω _e <ω_ϱa are analysed. It is shown that the monopole charges lead to observable effects. Finally, the results are applied to a typical pulsar.     

离子有限拉摩半径效应对低频漂移波本征模的影响

本文指出,对于S_y≡k_y²ρ_i²≥1的短波模,通常所用的漂移波本征方程是不自洽的,由此而得出“普适模是稳定的”结论也是不恰当的。我们在弱剪切条件(L_s/r_n>>[2T_im_i/Tm_e]^1/2)下导出了适合S_y≥1的方程,并讨论了其近似表式。在最低级近似下(主要是忽略k′ρ_i²项),证明了不存在γ≥0的不稳定模式。考虑一级修正项后,尚不能得出确定的结论。 关键词：     

Equilibrium and stability of the charged particles’ fluxes drifting crosswise to the strong magnetic field at the expense of the Hall charge separation

The current equilibrium is investigated, where the generation of the Hall electric field on the magnetic Debye radius r _B = B ₀/(4πen _e) is considered by the drifting of the relativistic electrons crosswise to the strong magnetic field. In this case, the electron propagation is possible at the distance d that is essentially larger than the electron radius of the backward reflection in the magnetic field r ₀ ? m _e v _z c/(eB ₀). The instability of the joint drift motion of ions and electrons is investigated for the frequency oscillation w much higher than the ion cyclotron frequency w _Bi and by 4π n _i m _i c ² ? B ₀ ² and (k · B ₀) = 0. It is shown that the resonance effects by the ion beam’s plasma frequency w ? kv ₀ = w _pi leads to the generation of the nonpotential perturbations with the characteristic increment Imw ～ 10^?1 ÷ 10^{? 2} w _pi. Estimates show that the instability, associated with the propagation of the high-energy ion beam through the strong magnetic field, can essentially be like the edge-localized mode in tokamaks.     

Coupled cluster calculations for the interstellar molecule HC3NH+

An accurate equilibrium structure has been established for the linear interstellar molecular cation HC₃NH⁺: r _1e(CH) = 1.0703Å, R _1e(C₍₁₎C₍₂₎) = 1.2097 Å, R _2e(C₍₂₎C₍₃₎) = 1.3509Å, R _3e(C₍₃₎N) = 1.1448 Å and r _2e(NH) = 1.0079Å. Ground-state rotational constants for less abundant isotopomers are predicted with an uncertainty of about 0.02 MHz. The equilibrium dipole moment of HC₃NH⁺ is calculated to be 1.61 D.     

Experimental studies of polarization of laser radiation in a rotating optical glass

The results of experiments on observation of rotation of the plane of polarization of coherent laser radiation with wavelength λ = 0.632991 μm after propagation through a rotating optical disk made of TF3 glass with refractive index n = 1.71250 are analyzed. The experiments were conducted at angle of ray incidence on the flat disk surface ?₀ = 60°, and the rotational speed of the disk was varied from 0 to 200 Hz in both directions. The results indicate that rotation of optically transparent, homogeneous, and isotropic dielectric causes rotation of linear polarization of the monochromatic electromagnetic plane wave by several tens of degrees. At a rotational speed of 3 Hz, the rotation of polarization reached Δφ = 70° for the vertical component of laser output polarization. The dependences of the angle of rotation of polarization and the degree of polarization of the rays on rotational speed are nonlinear and are attributed to the appearance of substantial anisotropic properties in a rotating dielectric.