Photoluminescence of the n+‐n‐i Submicron Structures of Gallium Arsenide

The special features of the photoluminescence of the n ⁺ni submicron structures of gallium arsenide are investigated. It is found that the character of the dependence of the fluorescence intensity on the thickness of the structure is determined by the relationship between three characteristic lengths: diffusional length, thickness of the n ⁺ layer, and depth of absorption of exciting radiation, whereas the decrease in the mobility of charge carriers in epitaxial layers leads to an increase in the fluorescence intensity of the structure, with exciting radiation being strongly absorbed.     

On the hall resistivity of nHgCdTe

We discuss the measurements of the Hall resistivity of nHgCdTe and InSb which have demonstrated the similarity of the electronic properties of these two materials. Gebhardt and Nimitz [1] dispute the validity of our results. We cite the evidence that confirms the correctness of our original observations.     

Parameterization of the nuclear Hulthén potentials

Within the formalism of supersymmetry-inspired factorization method, a two-term nuclear Hulthén potential has been developed and parameterized to reproduce the nucleon–nucleon scattering phase shifts for P and D partial wave states.     

Direct measurement of the interfacial barrier height of the manganite p–n heterojunction

A manganite p-n heterojunction composed of Lao.67Sro.33MnO3 film and 0.05 wt% Nb-doped SrTiO3 substrate is fabricated. Rectifying behavior of the junction well described by the Shockley equation is observed, and the transport properties of the interface are experimentally studied. A satisfactorily logarithmic linear dependence of resistance on temperature is observed in a temperature range of 150 K-380 K, and the linear relation between bias and activation energies deduced from the R - lIT curves is observed. According to activation energy, the interfacial barrier of the heterojunction is obtained, which is 0.91 eV.     

Preliminary computation of the gap eigenmode of shear Alfvén waves on the LAPD

Characterizing the gap eigenmode of shear Alfv′en waves(SAWs) and its interaction with energetic ions is important to the success of magnetically confined fusion. Previous studies have reported an experimental observation of the spectral gap of SAW on the on Large Plasma Device(LAPD)(Zhang et al. 2008 Phys. Plasmas 15 012103), a linear large plasma device(Gekelman et al. 1991 Rev. Sci. Instrum. 62 2875) possessing easier diagnostic access and lower cost compared with traditional fusion devices, and analytical theory and numerical gap eigenmode using ideal conditions(Chang 2014 Ph.D Thesis at Australian National University). To guide experimental implementation, the present work models the gap eigenmode of SAWs using exact LAPD parameters. A full picture of the wave field for previous experiment reveals that the previously observed spectral gap is not global but an axially local result. To form a global spectral gap, the number of magnetic mirrors has to be increased and stronger static magnetic field makes it clearer. Such a spectral gap is obtained for the magnetic field of B_0(z) = 1.2 + 0.6 cos[2π(z-33.68)/3.63] with 7.74-m magnetic beach. By introducing two types of local defects(corresponding to E_θ(z_0) = 0 and E'_θ(z_0) = 0 respectively), odd-parity and even-parity discrete eigenmodes are formed clearly inside the gap. The strength of these gap eigenmodes decreases significantly with collision frequency, which is consistent with previous studies. Parameter scans show that these gap eigenmodes can be even formed successfully for the field strength of B_0(z) = 0.2 + 0.1 cos[2π(z-33.68)/3.63] and with only four magnetic mirrors, which are achievable by the LAPD at its present status. This work can serve as a strong motivation and direct reference for the experimental implementation of the gap eigenmode of SAWs on the LAPD and other linear plasma devices.     

The spectrum of operators elliptic along the orbits of ℝ n actions

It is shown that a periodic elliptic operator on ⁿ has no eigenvalues off of the set of discontinuities of its spectral density function. The methods involve operator algebras and are based on a spectral duality principal first introduced by J. Bellisard and D. Testard. A version of the spectral duality theorem is proved which relates the point spectrum of a certain family of operators to the continuous spectrum of an associated family.Research sponsored in part by NSF grants     

Investigation of 238U in the (n,n′γ) reaction

An irradiation of ²³⁸U with a beam of reactor fast neutrons permits revealing about 550 gamma transitions associated with the respective (n, n′γ) reaction and with fission fragments. The use of all known data on gamma radiation from fission fragments makes it possible to identify gamma transitions belonging to ²³⁸U with a high probability. The scheme of levels and gamma transitions is composed for ²³⁸U. New levels (including those of spin-parity J ^π = 0⁺) at excitation energies below 2 MeV are proposed. The low-lying levels in the rotational band for two-phonon octupole excitations are determined. It is found that a hybrid state is formed upon the crossing of this band and the band based on two-quasiparticle excitations. This hybrid state must involve excitations of both types. A small value of the rotational-band parameter in the isomer of energy 2559.0(4) keV is explained by the contribution to this state from two-quasiparticle configurations belonging to the 1k _17/2 subshell. The same circumstance may also be responsible for an enhanced yield of ternary fission for this isomer.     

Excitation of Alfvén vortices in the ionosphere by the magnetospheric convection

We analyze conditions for excitation of ULF waves in the ionospheric Alfvén resonator (IAR), taking into account the altitude-inhomogeneous profile of the magnetospheric convection velocity. This profile is formed as a result of interaction of the convective flow with the neutral atmosphere at altitudes 90–150 km. ULF waves comprise oblique Alfvén waves, trapped into the IAR, and ionospheric drift waves, which are in resonance with them. These waves together form strongly anisotropic, closed current loops, whose scale along the magnetic field greatly exceeds their transverse scale, i.e., l_z ≫ l_⊥, and can be considered Alfvén vortices. Within the framework of the proposed model of the ionosphere, we study the instability threshold and the amplitude growth rate of the Alfvén vortices as functions of different parameters (wave vector k_22A5, angle between the wave vector and the convection velocity, ratio of the Alfvén-wave and Pedersen conductivities, etc.). Some estimates are given in application to the observed small-scale field-aligned currents in the auroral ionosphere. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 5, pp. 376–390, May 2008.     

Investigation of 166Er in the respective (n,n′γ) reaction

Physics of Atomic Nuclei - The spectrum, angular distribution, and linear polarization of gamma rays from the (n, n′γ) reaction on 166Er were measured in a beam of reactor fast neutrons....     

Numerical simulation of the multiple reversed shear Alfvén eigenmodes associated with the triangularity Alfvén gap

It was found that there are multiplicity of low shear toroidicity-induced Alfv′en eigenmodes in a zero beta limit if the inverse aspect ratio is larger than the magnetic shear at the mode location(Candy 1996 Phys. Lett. A 215 299). Because the reversed shear Alfv′en eigenmode(RSAE) and even the RSAE associated with the non-circular triangularity-induced Alfv′en eigenmode(NAE) gap(NAE–RSAE) usually reside near the shear-reversal point, the condition that the inverse aspect ratio is larger than the magnetic shear is naturally satisfied. For this reason, we numerically investigate the existence of multiplicity of core-localized NAE–RSAEs and mode characteristics in the present work. We firstly verify the existence of the multiplicity for zero beta plasma by using a D-shaped equilibrium. It is pointed out that, for a given toroidal mode number, the Alfv′en cascade spectrum accommodates down-sweeping and up-sweeping modes above and below the NAE range of frequencies. An analytical model for the existence of multiple RSAE modes is in good agreement with the simulation results. One notices that the triangularity has a greater effect on the odd-type modes than that on the even-type modes: the odd-type modes come into existence because of the plasma triangularity.     

Propagation of Alfvén surface waves along the ionospheric plasma slab with the effect of gravity

Ionospheric regions connecting the neutral gas atmosphere have been considered to be an incompressible plasma slab surrounded by incompressible plasma on one side and neutral gas on the other side. The effect of gravity on Alfvén surface waves in the slab geometry is studied. As a special case, the propagation of ASW along the plasma-neutral gas interface is also discussed. The existence of two modes of surface waves has been identified and their characteristic behaviour affected by the gravity has been discussed.     

A measurement of the total cross section of the capture reaction2H(n,t)γ atE n=25 MeV

The total cross section of the capture reaction²H(n, t) has been measured atE _n=25 MeV using a deuterium gas target and a scintillation counter telescope. The resulting value =(7.6±0.8) b is compared with existing photodisintegration data and theoretical calculations.     

On the “near to minimal” canonical realizations of the lie algebraC n

It is proved that canonical realizations of the Lie algebraC _n in the quotient division ringD _2(2n–2) of the Weyl algebraW _2(22–2) in 2n – 2 quantum canonical pairs are, in a definite sense, related to the standard minimal one inD _2n D _2(2n–2). Further, in any realization ofC _n inW _2(2n-1) all Casimir operators are realized by multiples of identity element.     

An approximate solution of the DKP equation under the Hulthén vector potential

Using the analytical NU technique as well as an acceptable physical approximation to the centrifugal term, the bound-state solutions of the Duffin-Kemmer-Petiau equation are obtained for arbitrary quantum numbers. The solutions appear in terms of the Jacobi Polynomials. Various explanatory figures and tables are included to complete the study.     

Alternation of the spin–orbit coupling in the 2Π ground state of HC n S (n = 1–12) radicals

First-order calculations of spin–orbit constants, dipole moments and carbon–sulphur distances have been performed for HC _n S (n = 1–12) radicals in the ²Π electronic ground state. It is found that these molecular properties alternate with even or odd numbers of carbon atoms in the chains and the spin–orbit constant A _SO is around ?300 cm^?1 for n even and about +120 cm^?1 for n odd throughout the series. This agrees with the experimentally determined value of about ?270 cm^?1 for HC₂S, but the theoretically predicted A _SO values are much larger than the values given for HC₃S and HC₄S from a fit of their millimeter-wave spectra. Values that were too low were also assumed in the analysis of the rotational spectra of n = 4–8.     

Heating of the solar corona by dissipative Alfvén solitons

Solar photospheric convection drives myriads of dissipative Alfvén solitons (hereinafter called alfvenons) capable of accelerating electrons and ions to energies of hundreds of keV and producing the x-ray corona. Alfvenons are exact solutions of two-fluid equations for a collisionless plasma and represent natural accelerators for conversion of the electromagnetic energy flux driven by convective flows into kinetic energy of charged particles in space and astrophysical plasmas. Their properties have been experimentally verified in the magnetosphere, where they accelerate auroral electrons to tens of keV.