Instability of layered quantum liquids: 6. Strongly correlated bosons

We calculate the local-field corrections G(q, q _z) for charged bosons at zero temperature in a superlattice with interlayer distance d. An analytical expression for the local-field correction is described. The sum-rule version of the self-consistent approach for the local-field correction is used to discuss the effects of correlation. The RPAparameter r _s and the ratio d/a* determine correlation effects. a* is the effective Bohr radius. The stability region for the Bose condensate r _s < r _sc as a function of d/a* is determined: r _sc ≈ (d/a*)^3/4. The ground-state energy of the layered Bose condensate is calculated and optical and acoustical plasmons are discussed. We predict a roton structure for optical plasmons for r _s > r _sr with r _sr ≈ 0.5 (d/a*)^3/4.     

Strange-quark matter within the Nambu-Jona-Lasinio model

The equation of state of baryon-rich quark matter is studied within the SU(3) Nambu-Jona-Lasinio model with flavor-mixing interaction. Possible bound states (strangelets) and chiral phase transitions in this matter are investigated at various values of the strangeness fraction r _s. Model predictions are very sensitive to the ratio of the vector and scalar coupling constants, ξ=G _V/G _S. At ξ=0.5 and zero temperature, the binding energy takes a maximum value of about 15 MeV per baryon at r _s?0.4. Such strangelets are negatively charged and have typical lifetimes of about 10^?7s. Calculations are performed at finite temperatures as well. According to these calculations, bound states exist up to temperatures of about 15 MeV. The model predicts a first-order chiral phase transition at finite baryon densities. The parameters of this phase transition are calculated as functions of r _s.     

Many-body effects in the binding energies of image states at surfaces

A study of the influence of many-body effects on binding energies and effective masses of image potential induced surface states is presented. The binding energies calculated using experimentally measured ε(ω) response functions show a dependence on the electron density different from that obtained using a plasmon model, and are in agreement with recent experimental data of diesen et al. [Phys. Rev. B33 (1986) 5241]. The effects of plasmon dispersion and single particle excitations on binding energies are evaluated with a simple model, and it is shown that they result in a strong cancellation in the range of r_s values where most experimental data have been obtained (r_s ≈ 3), if realistic values of the surface plasmon dispersion relation are used. Corrections to the effective masses due to many-body effects are shown to be of the order of 1%.     

Formation of textured Ni(200) and Ni(111) films by magnetron sputtering

The effect of the working gas pressure (P ≈ 1.33–0.09 Pa) and the substrate temperature (T_s ≈ 77–550 K) on the texture and the microstructure of nickel films deposited by magnetron sputtering onto SiO₂/Si substrates is studied. Ni(200) films with a transition type of microstructure are shown to form at growth parameters P ≈ 0.13–0.09 Pa and T_s ≈ 300–550 K, which ensure a high migration ability of nickel adatoms on a substrate. This transition type is characterized by a change of the film structure from quasi-homogeneous to quasi-columnar when a film reaches a critical thickness. Ni(111) films with a columnar microstructure and high porosity form at a low migration ability, which takes place at P ≈ 1.33–0.3 Pa or upon cooling a substrate to T_s ≈ 77 K.     

Charge exchange and excitation cross sections at collisions of alpha particles with be-like impurity oxygen ions in a plasma

The charge exchange and excitation cross sections at collisions of alphas with O⁴⁺(1s ²2s ²) impurity atoms in a hot plasma for striking energies E _c varying from 20 keV to 2 MeV are determined for the first time. The cross sections are calculated using the method of close-coupling equations with 13 singlet four-electron quasi-molecular states taken as a basis. The partial cross sections of charge transfer to the 1s, 2s, and 2p states of a He⁺ ion and for O⁴⁺(1s ²2s ²) → O⁴⁺(1s ²2lnl’) (n = 2, 3) electronic excitation of an oxygen ion are found. The maximal value of the charge exchange total cross section roughly equals 2.2 × 10^?16 cm² at E _c ≈ 0.7 MeV. The excitation total cross section has a maximum of ≈ 7.7 × 10^?16 cm² at E _c ≈ 80 keV for single-electron excitation and ≈6.5 × 10^?16 cm² at E _c ≈ 0.7 MeV for two-electron excitation.     

Correlation energy of 2-D electrons

The correlation energy and the Fermi momentum of an electron gas in 2-D are evaluated explicitly as functions of density. The ring diagram and first- and second-order exchange contributions are treated. In comparison with the 3-D case, the kinetic energy for the same r_s is approximately one-half and the exchange and correlation energies are somewhat larger. The ground state energy plotted against r_s shows a minimum at around r_s = 1.65 with a minimum value of ?0.9858 Ryd. If the third-order ring contribution is added, the curve is shifted upward. The correlation energy is ?0.6258 to order e⁴. The third-order ringw contribution increases this value almost linearly with r_s. The Fermi momentum decreases with r_s due to the contribution. Different from the 3-D case, no ln r_s term appears in the correlation energy within the approximation.     

On the ground state energy of a two-dimensional electron fluid

A new theory of the ground state energy of a two-dimensional electron fluid is presented. It is shown that the ring diagram contribution changes its analytical behavior atr _s =2^1/2, wherer _s is the usual density parameter defined by r_S = 1/a ₀(π n)^1/2,a ₀ being the Bohr radius andn is the electron density. For smallr _s , a high density series is obtained in agreement with the previous calculation. For larger _s , a hitherto unknown low density series is obtained. In the low density region, the first order exchange energy is completely cancelled out by a term from the ring contribution so that the ground state energy decreases in proportion tor _s ^?2/3 , followed byr _s ^/?4/3 and higher order terms. The energy is found to be minimum atr _s=1.4757, the minimum value being ?0.481915 Rydbergs.     

Screening of excitonic states by low-density 2D charge carriers in GaAs/AlGaAs quantum wells

Screening of excitonic states by a system of 2D electrons (or holes) in GaAs/AlGaAs single quantum wells is studied. With increasing concentration of 2D charge carriers, a threshold-type disappearance of excitonic states is observed in both luminescence and reflectance spectra. The higher the quality of the 2D system, the lower the corresponding threshold concentration. In the best systems, the collapse of excitonic states occurs at unexpectedly low electron densities n _e =5×10⁹ cm^?2, which correspond to the mean dimensionless distance between the particles r _s =8. This value far exceeds the threshold values observed for 3D systems (r _s ≈2), as well as the values obtained for quantum wells in previous studies. The problem of measuring the concentration of low-density 2D charge carriers in photoexcitation conditions is solved by applying the method of optical detection of the dimensional magnetoplasma resonance. This method provides reliable measurements of the density of a 2D system to the values about 10⁹ cm^?2.     

Particle mixing and charge asymmetric nuclear forces

The charge asymmetric effect of ?ω and πη electromagnetic mixing on the ¹S₀ NN potential is reviewed. It is found that the ?ω contribution dominates and leads to an n-n potential which is more attractive than the p-p potential. The shift in the scattering lengths is then calculated to be |a_nn|?|a_pp| ≈ 0.9 fm and the shift in effective ranges is r_nn?r_pp ≈ ?0.02 fm.     

Fusion through metallic deuterium. Part II

The possibility of attaining ²H(²H, n) ³He fusion in the metallic phase of deuterium is examined further. This scheme is based on the finite valuedness of the radial distribution at zero argument for an aggregate of charged bosons in a neutralizing background. Large deuteron wavefunction overlap is theoretically implied in the stable metallic liquid phase at r_s?0.21.     

Reinvestigation of microwave spectrum of dimethyl ether and rs structures of analogous molecules

Microwave spectra of dimethyl ether and its sixteen isotopic species have been measured. For species with singlet spectra, a least-squares analysis of observed transition frequencies gave rotational and five quartic centrifugal distortion constants. For species with multiplet spectra due to the methyl internal rotation, a least-squares analysis of observed multiplet frequencies gave not only unperturbed rotational and five quartic centrifugal distortion constants but also the quantities related to the methyl internal rotation. The r_s structures from (CH₃)₂O, CH₃OCD₃, and (CD₃)₂O species as the parent species, respectively, were compared with one another. The proposed r_s structure has been established from all the species measured and was compared with the r_s-like structure obtained by a diagnostic least-squares method and with the reported structure. The r_s structure of the present molecule was compared with the reported structures of dimethyl sulfide and dimethyl silane in relation to the tilt phenomenon. The r_s structure of dimethyl sulfide was revised based on the present comparison.     

Effect of bias voltage polarity of a substrate on the texture,microstructure, and magnetic properties of Ni films prepared by magnetron sputtering

The influence of the bias voltage polarity U_s on microstructure, crystallographic texture and magnetic properties has been investigated for Ni films with a thickness of ≈15–420 nm, which are obtained via magnetron sputtering at a working gas pressure P corresponding to the collision-deficient flight mode of atoms of the sputtered target between the target and the substrate. The Ni(111)-textured films have been shown to form at U_s ≈–100 V, whose microstructure and magnetic parameters are almost unchanged with a thickness. In contrast, the Ni(200) films are formed at U_s ≈ +100 V, whose magnetic properties and micro-structure depend significantly on the thickness d that manifests in a critical thickness d* ≈ 150 nm, when the structure of the film becomes inhomogeneous in the thickness, the remagnetization loops are changed from rectangular to supercritical with the formation of the band domain structure.     

Static structure factor of electrons around a heavy positively charged impurity in a one-component quantum rare plasma

An expression for the static structure factor,g ⁺⁻ (r), of electrons at a distancer from an infinitely heavy positively charged particle in a one component quantum rare plasma has been obtained in linear response theory using an appropriate quantum dielectric function of the rare plasma. The expression is a complicated function of the electron plasma frequency, Debye screening length andr, but reduces to that of classical plasma when quantum corrections are neglected. Forr<r _s (2r _s being the mean distance between two electrons), the temperature dependentg ⁺⁻ (r) has larger values in quantum case in comparison to that in classical situation and keeps increasing with decrease inr, more so at low temperatures when de-Broglie wavelength becomes larger and a considerable fraction ofr _s.     

A New Entropy Function to Analyze Isentropic Processes of Ideal Gases with Variable Specific Heats

A new entropy function s⁺ is defined in terms of the existing entropy function s° and temperature as s⁺ = s° − R lnT to facilitate the analysis of isentropic processes of ideal gases with variable specific heats. The function s⁺ also makes it possible to calculate the entropy changes of ideal gases during processes when volume information is available instead of pressure information and the variation of specific heats with temperature is to be accounted for. The introduction of the function s⁺ eliminates the need to use the dimensionless isentropic functions relative pressure P_r and relative specific volume v_r of ideal gases and to tabulate their values. The P_r and v_r data are often confused with pressure and specific volume, with an adverse effect on the study of the second law of thermodynamics. The new s⁺ function nicely complements the existing s° function in entropy change calculations: the former is conveniently used when volume information is given while the latter is used when pressure information is available. Therefore, the introduction of the new entropy function s⁺ is expected to make a significant contribution to the thermodynamics education and research by streamlining entropy analysis of ideal gases.     

二维电子体系在高密度下的稳定性

本文计算了高密度的二维电子体系的边缘能(将二维体系沿某一直线解离成两片时,形成单位长度新边缘所需要的能量)。结果发现,当r_ss^(c)(约0.415)时,边缘能变负,从而表明在高密度下,二维电子气的基态有可能发生不稳。我们分别讨论了二维非束缚的电子气和束缚的电子气基态的稳定性,并在一个简化的模型下给出了束缚的电子气基态稳定性的判据。 关键词：     

Initiation and development of nanosecond discharges in liquids

The initiation and development of discharges in purified water and hexane were studied for pulse rise times ofΤ _r ≈ 2?3 nsec and pulse lengths ofΤ _p≈10–50 nsec by an oscilloscopic method and with an electron-optical image converter. The results are compared with data on the nanosecond breakdown of gases. A physical interpretation is offered for the observed behavior.     

Chirality and its breaking in a new theory of hadrons

We show that in Anisotropic Chromo-Dynamics (ACD), a new approach to the dynamics of coloured, confined quarks, the π-meson is a qq?-bound state very close to the Nambu-Goldstone boson of a spontaneously broken chiral symmetry. We calculate the “current” quark masses and obtain m_u⁽⁰⁾ ≈ m_d⁽⁰⁾ ≈ 18 MeV, and m_s⁽⁰⁾ ≈ 123 Mev, in disagreement with the usual “strong PCAC” Ansatz.     

On the low-temperature thermal conductivity of Ni-doped Al2O3

An attempt is made to explain the lower resonance anomaly in the thermal conductivity of Ni-doped Al₂O₃ by using τ_r ～ ω^-4s(ω² ? ω²_r)². An agreement between theory and experiment needs s = 0.71, and this is interpreted to mean that the frequency dependence of impurity-phonon coupling is approximately described by ω^0.71 for phonons having frequencies in close neighbourhood of ω_r.     

Charged <Emphasis Type="Italic">ρ</Emphasis>-meson production in neutrino-induced reactions at &lt;<Emphasis Type="Italic">E</Emphasis><Subscript><Emphasis Type="Italic">ν</Emphasis></Subscript>&gt;≈ 10 GeV

The production of charged ρ mesons on nuclei and nucleons is investigated in charged current neutrino interactions at moderate energies (〈E _〉 ≈ 10 GeV), using the data obtained with SKAT bubble chamber. No strong nuclear effects are observed in ρ ⁺ and ρ ^? production. The fractions of charged and neutral pions originating from ρ decays are obtained and compared with higher-energy data. From analysis of the obtained and available data on ρ ⁺ and K*⁺(892) neutrino production, the strangeness suppression factor is extracted: λ _s = 0.18 ± 0.03. Estimation is obtained for cross section of coherent ρ ⁺ neutrino production on nuclei.     

Universal multiplicity hypothesis of QCD: Bounds on quark gluon coupling,quark mass and confinement region

Assuming the validity of the universal multiplicity hypothesis of quantum chromodynamics, we estimate bounds on quark gluon coupling (α_S) and quark mass (m) from the experimental data on charged hadron multiplicities. We obtain 0.3 < α_S < 0.5 and m ≈ 100 MeV. Our analysis also suggests the universal quark confinement region to be ≈ O (m_π^?1). Comparison with experiment is made for both the hadronic and leptonic induced reactions.