527 research outputs found
Super Tonks-Girardeau state in an attractive one-dimensional dipolar gas
The ground state of a one-dimensional (1D) quantum gas of dipoles oriented
perpendicular to the longitudinal axis, with a strong 1/x^3 repulsive
potential, is studied at low 1D densities . Near contact the dependence of
the many-body wave function on the separation x_{jl} of two particles reduces
to a two-body wave function \Psi_{rel}(x_{jl}). Immediately after a sudden
rotation of the dipoles so that they are parallel to the longitudinal axis,
this wave function will still be that of the repulsive potential, but since the
potential is now that of the attractive potential, it will not be stationary.
It is shown that as nd^2 -> 0 the rate of change of this wave function
approaches zero. It follows that for small values of nd^2, this state is
metastable and is an analog of the super Tonks-Girardeau state of bosons with a
strong zero-range attraction. The dipolar system is equivalent to a spinor
Fermi gas with spin components \sigma_{\uparrow}=\perp (perpendicular to
the longitudinal axis) and \sigma_{\downarrow}=|| (parallel to the longitudinal
axis). A Fermi-Fermi mapping from spinor to spinless Fermi gas followed by the
standard 1960 Fermi-Bose mapping reduces the Fermi system to a Bose gas.
Potential experiments realizing the sudden spin rotation with ultracold dipolar
gases are discussed, and a few salient properties of these states are
accurately evaluated by a Monte Carlo method.Comment: 5 pages, 2 figures, revtex4. Published versio
Fifty years of the Glauber diffraction theory
In this minireview a historical excursus in theoretical studies related to
the Glauber diffraction theory has been presented with an accent on the recent
developments in this subject.Comment: 22 pages, 4 figures, in russian;v2: an atempt to improve hyphenatio
Quantum phase transition in a two-dimensional system of dipoles
The ground-state phase diagram of a two-dimensional Bose system with
dipole-dipole interactions is studied by means of quantum Monte Carlo
technique. Our calculation predicts a quantum phase transition from gas to
solid phase when the density increases. In the gas phase the condensate
fraction is calculated as a function of the density. Using Feynman
approximation, the collective excitation branch is studied and appearance of a
roton minimum is observed. Results of the static structure factor at both sides
of the gas-solid phase are also presented. The Lindeman ratio at the transition
point comes to be . The condensate fraction in the gas phase
is estimated as a function of the density.Comment: 4 figures v.3 One citation added, updated Fig.4. Minor changes
following referee's and editor's comment
<i>N,N</i>-bis-(dimethylfluorosilylmethyl)amides of <i>N</i>-organosulfonylproline and sarcosine: synthesis, structure, stereodynamic behaviour and <i>in silico</i> studies
(O→Si)-Chelate difluorides R3R2NCH(R1)C(O)N(CH2SiMe2F)2 (9a–c, R1R2 = (CH2)3, R3 = Ms (a), Ts (b); R1 = H, R2 = Me, R3 = Ms (c)), containing one penta- and one tetracoordinate silicon atoms were synthesized by silylmethylation of amides R3R2NCH(R1)C(O)NH2, subsequent hydrolysis of unstable intermediates R3R2NCH(R1)C(O)N(CH2SiMe2Cl)2 (7a–c) into 4-acyl-2,6-disilamorpholines R3R2NCH(R1)C(O)N(CH2SiMe2O)2 (8a–c) and the reaction of the latter compounds with BF3·Et2O. The structures of disilamorpholines 8a,c and difluoride 9a were confirmed by an X-ray diffraction study. According to the IR and NMR data, the O→Si coordination in solutions of these compounds was weaker than that in the solid state due to effective solvation of the Si–F bond. A permutational isomerisation involving an exchange of equatorial Me groups at the pentacoordinate Si atom in complexes 9a–c was detected, and its activational parameters were determined by 1H DNMR. In silico estimation of possible pharmacological effects and acute rat toxicity by PASS Online and GUSAR Online services showed a potential for their further pharmacological study
Collective and static properties of model two-component plasmas
Classical MD data on the charge-charge dynamic structure factor of
two-component plasmas (TCP) modeled in Phys. Rev. A 23, 2041 (1981) are
analyzed using the sum rules and other exact relations. The convergent power
moments of the imaginary part of the model system dielectric function are
expressed in terms of its partial static structure factors, which are computed
by the method of hypernetted chains using the Deutsch effective potential.
High-frequency asymptotic behavior of the dielectric function is specified to
include the effects of inverse bremsstrahlung. The agreement with the MD data
is improved, and important statistical characteristics of the model TCP, such
as the probability to find both electron and ion at one point, are determined.Comment: 25 pages, 6 figures, 5 tables. Published in Physical Review E
http://link.aps.org/abstract/PRE/v76/e02640
Tensor analyzing power Ayy in deuteron inclusive breakup at large Pt and spin structure of deuteron at short internucleonic distances
The Ayy data for deuteron inclusive breakup off hydrogen and carbon at a
deuteron momentum of 9.0 GeV/c and large Pt of emitted protons are presented.
The large values of Ayy independent of the target mass reflect the sensitivity
of the data to the deuteron spin structure. The data obtained at fixed and
plotted versus Pt clearly demonstrate the dependence of the deuteron spin
structure at short internucleonic distances on two variables. The data are
compared with the calculations using Paris, CD-Bonn and Karmanov's deuteron
wave functions.Comment: 4 pages, 2 figures, talk given at the SPIN2004 Conf., 10-16 Oct.
2004, Triest, Ital
Pairing of charged particles in a quantum plasmoid
We study a quantum spherically symmetric object which is based on radial
plasma oscillations. Such a plasmoid is supposed to exist in a dense plasma
containing electrons, ions, and neutral particles. The method of creation and
annihilation operators is applied to quantize the motion of charged particles
in a self-consistent potential. We also study the effective interaction between
oscillating particles owing to the exchange of a virtual acoustic wave, which
is excited in the neutral component of plasma. It is shown that this
interaction can be attractive and result in the formation of ion pairs. We
discuss possible applications of this phenomenon in astrophysical and
terrestrial plasmas.Comment: 17 pages, no figures, two columns, LaTeX2e; paper was significantly
revised; title was changed; 16 new references were included; the discussion
on ion-acoustic waves was added to Sec. 2; Secs. 3 and 4 were shortened; a
more detailed discussion was added to Sec. 7; accepted for publication to
J.Phys.
Theory of Exciton Migration and Field-Induced Dissociation in Conjugated Polymers
The interplay of migration, recombination, and dissociation of excitons in
disordered media is studied theoretically in the low temperature regime. An
exact expression for the photoluminescence spectrum is obtained. The theory is
applied to describe the electric field-induced photoluminescence-quenching
experiments by Kersting et al. [Phys. Rev. Lett. 73, 1440 (1994)] and Deussen
et al. [Synth. Met. 73, 123 (1995)] on conjugated polymer systems. Good
agreement with experiment is obtained using an on-chain dissociation mechanism,
which implies a separation of the electron-hole pair along the polymer chain.Comment: 4 pages, RevTeX, 2 Postscript figure
Hopping mobility of charge carriers in disordered organic host-guest systems: Dependence on the charge-carrier concentration
FIELD ELECTRON EMISSION FROM A NICKEL-CARBON NANOCOMPOSITE
The field-emission properties of nanocomposite films comprised of 10 -20 nm-sized nickel particles immersed in a carbon matrix were investigated. The films were deposited onto silicon substrates by means of a metal-organic chemical vapor deposition (MOCVD) method. The composite's structure was controlled via deposition process parameters. Experiments demonstrated that the composite films can efficiently emit electrons, yielding current densities of up to 1.5 mA/cm 2 in electric fields below 5 V/µm. Yet, good emission properties were only shown in films with low effective thickness, when nickel grains did not form a solid layer, but left a part of the substrate area exposed to the action of the electric field. This phenomenon can be naturally explained in terms of the two-barrier emission model
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