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1.
S.M.S. da Costa M.H.F. Bettega 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,3(1):67-71
We report elastic integral, momentum transfer and differential cross sections for electron scattering by N2O for energies up to 50 eV. These results were obtained at the static-exchange approximation with the Schwinger Multichannel
Method with Pseudopotentials [M.H.F. Bettega, L.G. Ferreira and M.A.P. Lima, Phys. Rev. A 47, 1111 (1993)]. In general our results show good agreement with experimental data and with other theoretical results but some
discrepancies are found. We have also found a shape resonance around 4 eV in agreement with previous calculations using the R-matrix Method of Sarpal et al. [J. Phys. B 29, 857 (1996)]. On the other hand, the existence of a resonance at about 13 eV, clearly seen by the Schwinger Variational Iterative Method [Michelin et al., J. Phys. B 29, 2115 (1996)], can not be confirmed by our calculations. At this energy, our cross sections show a broad bump with no clear resonant behavior given by the eigenphase sum.
Received: 13 November 1997 / Revised: 13 March 1998 / Accepted: 9 April 1998 相似文献
2.
A. Fioretti E. Arimondo A. Crubellier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):219-225
The measurements of fine-structure changing collisions in a cesium magneto-optical trap, reported in a previous work [A. Fioretti
et al., Phys. Rev. A 55, R3999 (1997)], are reanalyzed within a model based on the flux enhancement effect, which takes place in cold atomic collisions.
In the present analysis, we consider the cooperative effect of the long-range and the shorter-range excitation by the strong
trap laser. We evidence also the important role of the hyperfine structure of the Cs2 molecular levels asymptotically connected to the ground-state and excited-state dissociation limits.
Received 22 July 1999 and Received in final form 4 May 2000 相似文献
3.
K. Mølmer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):301-305
We discuss the possibility of preparing an atomic sample of atoms with minimum fluctuations in the difference between populations
of two levels. A first scheme involves absorption of twin beams of light, and it presents a variant of a recent proposal for
atomic spin squeezing within an excited state manifold [Kuzmich et al., Phys. Rev. Lett. 79, 4782 (1997)]. A second scheme involves atoms with two stable states, and we suggest that by use of quantum non-demolition
detection and feed-back optical pumping, we may ensure a perfect agreement between the number of atoms in these two states.
Received: 14 May 1998 / Revised: 10 August 1998 / Accepted: 8 October 1998 相似文献
4.
J. P. Santos F. Parente 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):339-350
Total ionization cross sections of neutral phosphorus, arsenic,
antimony, and bismuth atoms by electron impact are reported and
compared to the only available experimental results by Freund et al. [Phys. Rev. A 41, 3575 (1990)]. These calculations take into account the possibilities that some
target atoms used in the experiments were in metastable states close
to the ground state, the excitation-autoionization of nsnp4
excited states may be substantial, and the ions produced in
experiments may be in excited, low-lying metastable states. The cross sections for direct ionization calculations are based
on
the BEB model by Kim and Rudd [Phys. Rev. A 50, 3954 (1994)].
Plane-wave Born cross sections scaled by the method developed by Kim
[Phys. Rev. A 64, 3954 032713 (2001)] are used to determine the
contributions from excitation-autoionization. The combination of the BEB model and the scaled Born cross sections
is in agreement with the experimental data by Freund et al. These theoretical data are useful to experimentalists and can
be
used to complete data tables needed for plasma or astrophysical
studies. 相似文献
5.
Y.B. Duan L. Wang W.J. Qian 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(1):25-29
A non-partial-wave Coulomb-Born theory is recently formulated to treat the excitation of many-electron atomic ions for impact
by an arbitrary charged particle [Y.B. Duan et al., Phys. Rev. A 56, 2431 (1997)]. The multiple expansion of the transition matrix element is decomposed into the target form factor and the
projectile form factor. These are the matrix elements of the tensor operators between quantum states so that any complicated
wave function for the target ion can be employed. In this formal theory, an infinitesimally small positive quantity is introduced artificially to guarantee the convergence of integrals. As a supplementary part of the theory, we discuss how
to choose the value of . It is found that the should be taken as functions of the momentum transfer and multipolarity . Illustrations are carried out by calculating the cross-sections for some typical transitions n
a
l
a
-n
b
l
b
of hydrogen-like ions for impact by electron, positron, and proton, respectively. The resulting cross-sections are in good
agreement with ones produced by using a method available for ion targets with Slater-type orbitals [N.C. Deb, N.C. Sil, Phys.
Rev. A 28, 2806 (1993)]. Comparisons demonstrate that the Coulomb-Born theory with non-partial wave analysis provides a powerful method
to treat the excitation of many-electron atomic ions impact by an arbitrary charged particle.
Received 6 April 1999 相似文献
6.
W. Ekardt W.-D. Schöne R. Keyling 《Applied Physics A: Materials Science & Processing》2000,71(5):529-535
Experience has shown that theoretically determined lifetimes of bulk states of hot electrons in real metals agree quantitatively
with the experimental ones, if theory fully takes into account the crystal structure and many-body effects of the investigated
metal, i.e., if the Dyson equation is solved at the ab initio level and the effective electron–electron interaction is determined beyond the plasmon-pole approximation. Therefore the
hitherto invoked transport effect [Knoesel et al.: Phys. Rev. B 57, 12812 (1998)] does not seem to exist. In this paper we show that likewise neither virtual states [Hertel: et al. Phys. Rev.
Lett. 76, 535 (1996)] nor damped band-gap states [Ogawa: et al.: Phys. Rev. B 55, 10869 (1997)] exist, but that the hitherto unexplained d-band catastrophe in Cu [Cu(111), Cu(110)] can be naturally resolved
by the concept of the transient exciton. This is a new quasiparticle in metals, which owes its existence to the dynamical character of dielectric screening at the microscopic level. This means that excitons, though they do not exist under stationary
conditions, can be observed under ultrafast experimental conditions.
Received: 30 March 2000 / Accepted: 2 September 2000 / Published online: 12 October 2000 相似文献
7.
N. Stevanović D. Nikezić 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):397-406
Collision of swift ions with atoms was considered in this paper. The
projectile and target atoms were modeled as assemblies of quantum
oscillators and it was assumed that both, target and projectile could be
excited or ionized, without charge exchange. The model presented here is an
extension of the one given by Sigmund and Haagerup [Phys. Rev. A 34, 892 (1986)]. The number of electrons bound to the projectile, as a function of the projectile velocity,
was used from Cabrera-Trujillo et al. [Phys. Rev. A 55, 2864 (1997)]. Contributions to energy loss from excitation of the projectile and targets were separately considered. It
has been found that projectile excitation contributes up to 20% to the
total energy loss in the lower energy region. Comparisons with other
authors, including SRIM 2003, are also given and good agreement was found. 相似文献
8.
C.-S. Yu H.-S. Song 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(1):147-151
In this paper, an intuitive approach is employed to
generalize the full separability criterion of tripartite quantum
states of qubits to the higher-dimensional systems [Phys. Rev. A
72, 022333 (2005)]. A distinct characteristic of the
present generalization is that less restrictive conditions are
needed to characterize the properties of full separability.
Furthermore, the formulation for pure states can be conveniently
extended to the case of mixed states by utilizing the Kronecker
product approximate technique. As applications, we give the analytic
approximation of the criterion for weakly mixed tripartite quantum
states and investigate the full separability of some weakly mixed
states. 相似文献
9.
I. M. Herbauts S. Bettelli H. Hübel M. Peev 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):395-406
Some MIT researchers [Phys. Rev. A
75, 042327 (2007)] have recently claimed that
their implementation of the Slutsky-Brandt attack [Phys. Rev. A
57, 2383 (1998); Phys. Rev. A 71, 042312 (2005)] to
the BB84 quantum-key-distribution (QKD) protocol puts the security of this
protocol “to the test” by simulating “the most powerful
individual-photon attack” [Phys. Rev. A 73, 012315
(2006)].
A related unfortunate news feature by a
scientific journal [G. Brumfiel, Quantum cryptography is hacked, News @ Nature (april 2007); Nature 447, 372 (2007)]
has spurred some concern in the QKD community and among the general public
by misinterpreting the implications of this work. The present article
proves the existence of a stronger individual attack on QKD protocols with
encrypted error correction, for which tight bounds are shown, and clarifies
why the claims of the news feature incorrectly suggest a contradiction with
the established “old-style” theory of BB84 individual attacks.
The full implementation of a quantum cryptographic protocol includes a
reconciliation and a privacy-amplification stage, whose choice alters in
general both the maximum extractable secret and the optimal eavesdropping
attack. The authors of [Phys. Rev. A
75, 042327 (2007)] are concerned only with the error-free
part of the so-called sifted string, and do not consider faulty bits,
which, in the version of their protocol, are discarded. When using the
provably superior reconciliation approach of encrypted error correction
(instead of error discard), the Slutsky-Brandt attack is no more optimal
and does not “threaten” the security bound derived by Lütkenhaus [Phys. Rev. A 59, 3301 (1999)].
It is shown that the method of Slutsky and collaborators [Phys. Rev. A
57, 2383 (1998)] can
be adapted to reconciliation with error correction, and that the optimal
entangling probe can be explicitly found. Moreover, this attack fills
Lütkenhaus bound, proving that it is tight (a fact which was not
previously known). 相似文献
10.
S. Yuan J.-Y. Gao 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(2):267-272
A new scheme of the influence of quantum interference on the spontaneous emission in a coherently driven three-level medium
is presented in this paper. The results are the same with that discussed by [S.-Y. Zhu, L.M. Narducci, M.O. Scully, Phys.
Rev. A 52, 4791 (1995)] under resonance conditions, but they are different when the driven field is detuned.
Received 8 September 1999 and Received in final form 13 January 2000 相似文献
11.
Th. Baxevanis Th. Katsaounis 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):153-157
We present a detailed statistical analysis of the size and temporal occurrence of burst sequences in the creep rupture of
a proposed linear viscoelastic fiber bundle model. According to the model, the burst sequences of fiber breaks display a power law asymptotic
behavior analogous to that of the static-fracture [Kloster et al., Phys. Rev. E 56, 2615, (1997)]. Moreover, power law asymptotics apply to inter-arrival times between successive bursts with a universal exponent close to unity. 相似文献
12.
P. Sjölund S. J.H. Petra C. M. Dion H. Hagman S. Jonsell A. Kastberg 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):381-388
We present here a detailed study of the behaviour of a three dimensional Brownian motor based on cold atoms in a double optical
lattice [P. Sj?lund et al., Phys. Rev. Lett. 96, 190602 (2006)]. This includes both experiments and numerical simulations of a Brownian particle. The potentials used are
spatially and temporally symmetric, but combined spatiotemporal symmetry is broken by phase shifts and asymmetric transfer
rates between potentials. The diffusion of atoms in the optical lattices is rectified and controlled both in direction and
speed along three dimensions. We explore a large range of experimental parameters, where irradiances and detunings of the
optical lattice lights are varied within the dissipative regime. Induced drift velocities in the order of one atomic recoil
velocity have been achieved. 相似文献
13.
E. Luc-Koenig M. Aymar M. Millet J.-M. Lecomte A. Lyras 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(2):205-223
We have investigated theoretically the asymmetrical photoionization yields into the 6s
1/2, 5d
3/2 and 5d
5/2 continuum channels of atomic barium observed by Wang, Chen and Elliott [Phys. Rev. Lett. 77, 2416 (1996)] in the study of coherent control through two-color resonant interfering paths. The atomic parameters obtained
from a theoretical approach based on a combination of jj-coupled eigenchannel R-matrix and Multichannel Quantum Defect Theory are used to analyze the photoionization spectra from the and 6s7p
states with polarized light beams. The studied energy range includes the 6p7p autoionizing resonances. The dynamics of the two-color photoionization is governed by the coherent excitation of the 6s6p and intermediate states. This excitation is described as an adiabatic process in the rotating wave approximation. The influence
of the radiative decay, spatial distribution of the intensities of the laser beams and hyperfine interaction is discussed.
Received 28 September 1999 相似文献
14.
R.S. Mendes S.F. Kwok E.K. Lenzi J.N. Maki 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(2):353-359
By using integral representations the perturbation expansion and the Bogoliubov inequality in nonextensive Tsallis statistics
are investigated in a unified way. This procedure extends the analysis performed recently by Lenzi et al. [Phys. Rev. Lett. 80, 218 (1998)] to the quantum (discrete spectra) case, for q<1. An example is presented in order to illustrate the method.
Received 19 November 1998 相似文献
15.
S. Pirandola S. Mancini D. Vitali P. Tombesi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,37(2):283-290
Recently it has been proposed to construct quantum error-correcting codes
that embed a finite-dimensional Hilbert space in the infinite-dimensional
Hilbert space of a system described by continuous quantum variables [D.
Gottesman et al., Phys. Rev. A 64, 012310 (2001)]. The
main difficulty of this continuous variable encoding relies on the physical
generation of the quantum codewords. We show that ponderomotive interaction
suffices to this end. As a matter of fact, this kind of interaction between
a system and a meter causes a frequency change on the meter proportional to
the position quadrature of the system. Then, a phase measurement of the
meter leaves the system in an eigenstate of the stabilizer generators,
provided that system and meter's initial states are suitably prepared. Here
we show how to implement this interaction using trapped ions, and how the
encoding can be performed on their motional degrees of freedom. The
robustness of the codewords with respect to the various experimental
imperfections is then analyzed. 相似文献
16.
G. Duchateau E. Cormier R. Gayet 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(2):191-196
A simple theoretical approach based on Coulomb-Volkov states is introduced to predict ionisation of atoms by intense laser
pulses in cases where the effective interaction time does not exceed one or two optical cycles [M. Nisoli et al., Opt. Lett. 22, 522 (1997)]. Under these conditions, the energy distributions of ejected electrons predicted by this non-perturbative approach
are in very good agreement with “exact" results obtained by a full numerical treatment. The agreement is all the better that
the principal quantum number of the initial state is high. For very strong fields, most electrons are ejected at an energy
which is close to the classical kinetic energy that would be transferred to free electrons by the electromagnetic field during
the pulse. The power of the present approach appears when keV. In this region, full numerical treatments become very lengthy and finally do not converge. However, the present Coulomb-Volkov
theory still makes reliable predictions in very short computer times.
Received 19 November 1999 and Received in final form 19 January 2000 相似文献
17.
Y. Caglar S. Ilican M. Caglar 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(3):251-256
It has recently been shown that growth of a multilayer
structure with one or more delta-layers at high temperature leads to
spreading and asymmetrization of the dopant distribution [see, for
example, E.F.J. Schubert, Vac. Sci. Technol. A. 8, 2980 (1990), A.M. Nazmul, S. Sugahara, M. Tanaka, J. Crystal Growth 251, 303 (2003); R.C. Newman, M.J. Ashwin, M.R. Fahy, L. Hart, S.N. Holmes, C. Roberts, X. Zhang, Phys. Rev. B 54, 8769 (1996); E.F. Schubert, J.M. Kuo, R.F. Kopf, H.S. Luftman, L.C. Hopkins, N.J. Sauer, J. Appl. Phys. 67, 1969 (1990); P.M. Zagwijn, J.F. van der Veen, E. Vlieg, A.H. Reader, D.J. Gravesteijn, J. Appl. Phys. 78, 4933 (1995); W.S. Hobson, S.J. Pearton, E.F. Schubert, G. Cabaniss, Appl. Phys. Lett. 55, 1546 (1989); Delta Doping of Semiconductors, edited by E.F. Schubert (Cambridge University Press, Cambridge, 1996); Yu.N. Drozdov, N.B. Baidus', B.N. Zvonkov, M.N. Drozdov,
O.I. Khrykin, V.I. Shashkin, Semiconductors 37, 194 (2003); E. Skuras, A.R. Long, B. Vogele, M.C. Holland, C.R. Stanley, E.A. Johnson, M. van der Burgt, H. Yaguchi, J.
Singleton, Phys. Rev. B 59, 10712 (1999); G. Li, C. Jagadish, Solid-State Electronics 41, 1207 (1997)]. In this
work analytical and numerical analysis of dopant dynamics in a
delta-doped area of a multilayer structure has been accomplished
using Fick's second law. Some reasons for asymmetrization of a
delta-dopant distribution are illustrated. The spreading of a
delta-layer has been estimated using example materials of a
multilayer structure, a delta-layer and an overlayer. 相似文献
18.
R. K. Varma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(2):39
Matter wave interference effects on the macro-scale predicted by the author in charged particle dynamics in a magnetic field
[R.K. Varma, Phys. Rev. E 64, 036608 (2001)], and observed subsequently [R.K. Varma, A.M. Punithavelu, S.B. Banerjee, Phys. Rev. E 65, 026503 (2002); R.K. Varma, S.B. Banerjee, Phys. Scr. 75, 19 (2007)] have been shown here to be an interesting consequence of quantum entanglement between the parallel and perpendicular
degrees of freedom of the particle. Treating the problem in the framework of the inelastic scattering theory, it is shown
that these macro-scale matter waves are generated in the ‘parallel’ degree of freedom as a modulation of the plane wave state
of the particle along the field concomitantly with the excitation of Landau levels in the perpendicular degree of freedom
in an inelastic scattering episode. We highlight here the role of quantum entanglement leading to the generation of this macro-scale
quantum entity which has been shown to exhibit observable consequences. This case also exemplifies a situation exhibiting
quantum entanglement on the macro-scale. 相似文献
19.
M.A. Kornberg V.D. Rodríguez 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):221-224
We present calculations of the fivefold differential cross-section (FDCS) for double photoionization of helium at excess energies
of 6 and 20 eV above threshold. Our results are obtained using for the final double-continuum state a product of three Coulomb
wave functions, with the Sommerfeld parameters modified to describe the strength of interaction of any two particles affected
by the third particle. Our calculations are compared with recent absolute measurements by D?rner et al. (Phys. Rev. A 57, 1074 (1998)), both in coplanar and non-coplanar geometries. Very good agreement is obtained for the shape of the angular
distributions, and differences in the absolute magnitude exist in comparison with the standard choice of Sommerfeld parameters.
Received: 17 July 1998 / Received in final form and Accepted: 23 October 1998 相似文献
20.
We present an interferometer for simulating the quantum network for quantum estimation proposed by A.K. Ekert et al. [A.K. Ekert, C.M. Alves, D.K.L. Oi, M. Horodecki, P. Horodecki, L.C. Kwek, Phys. Rev. Lett. 88 (2002) 217901]. We experimentally perform overlap measurements of two single-qubit states with linear optical elements. The scheme is generalized to perform estimation of Trρ3. 相似文献