共查询到20条相似文献,搜索用时 31 毫秒
1.
G. M. Petrov J. Davis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):629-639
The dynamics of clusters irradiated by a high-intensity ultrashort pulse
laser has been studied using a fully relativistic three-dimensional
Molecular Dynamics Model. A fast three-dimensional tree algorithm for
computing the electrostatic force has been developed and compared with the
conventional particle-particle method. The particle-particle method requires
computation time, which scales as O(Np
2), and it is faster for small
number of particles Np <103. In the opposite case of relatively large
ensemble of particles Np >103, the preferred method is the tree
algorithm whose computation time scales as O(Np log Np). The tree
algorithm has been benchmarked against the particle-particle method for
clusters composed of xenon and deuterium atoms and its accuracy and
computation time have been analyzed. The optimum free parameter of the tree
method has been determined to be θ≈0.5. We addressed the
effects of boundary conditions by studying the contribution of adjacent
clusters to the total electromagnetic force exerted on individual particles.
We found that the adjacent clusters play a minor role in the overall cluster
dynamics. 相似文献
2.
Summary A general scheme is proposed for the interpretation of the phenomena involving low-energy hydrogen-isotope fusion. This scheme
is especially developed for the interpretation of the fusion rate observed after the impact of heavy-water clusters (D2O)
n
, 25≲n≲1350, onto targets of titanium deuteride TiD. It is shown that 1) the impinging energy of large clusters or molecules is
equiparted among a lot of target atoms which are brought in collective motion; 2) data can conveniently be represented in
an Arrhenius plot; 3) this plot suggests that fusion is a thermally activated process from a metastable precursor; 4) the
activation energy for the precursor formation isE
*≃2E
0 (E
0 being the electron binding energy in the hydrogen atom), and 5) the activated precursor can reasonably be identified with
the metastable binuclear heliumlike (D+D+)2e− atom. 相似文献
3.
We have used EPR to study oak bark, bulb onion peel, and their aqueous extracts. We have established that their paramagnetic
properties are determined by at least four types of paramagnetic centers: semiquinone radicals, Fe3+ ions, and two types of Mn2+ ions. We have observed that metal ions are extracted by water from the plant raw material without any change in their original
coordination environment. The aqueous extracts were subjected to oxidative processes: mild oxidation in the dried state, strong
oxidation when stored as solutions. We have shown that when the solutions are stored, the oxidation reaction is catalyzed
by the metal ions and is accompanied by formation of semiquinone radicals.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 440–445, May–June, 2009. 相似文献
4.
We discuss the condition for the presence of isoscalar parity violating neutral currents and notice that it is present in
most gauge-theoretic models of weak interactions. We investigate the possibility of testing its presence in e+e− colliding beams and find that parity violation in the reaction e+e−→Λ°Λ° would provide an unambiguous test for such a current. 相似文献
5.
V. I. Tsaryuk K. P. Zhuravlev V. F. Zolin V. A. Kudryashova J. Legendziewicz R. Szostak 《Journal of Applied Spectroscopy》2007,74(1):51-59
We discuss the possibility of optimizing the brightness of luminescence for phenylcarboxylates, naphthylcarboxylates, and
indolylcarboxylates of europium and terbium and their adducts with 1,10-phenanthroline and 2,2′-bipyridine by modifying the
ligands. We have studied the efficiency of luminescence and luminescence excitation. We consider the effect of blocking energy
transfer from the ligands to the Eu3+ and Tb3+ ions by methylene (-CH2-) bridges dividing the π-electron system of the ligands into two parts and by the electronacceptor nitro group (-NO2). We have analyzed the pathways for transfer and degradation of the excitation energy at 77 K and 300 K. From the phosphorescence
spectra of gadolinium salts, we have determined the energies of the lowest excited triplet states of the ligands. We consider
the effect of the relative positions of the triplet levels of the ligands and the excited levels of the Eu3+ and Tb3+ ions on the luminescence efficiency. We found channels for dissipation of the excitation energy via the ππ* and nπ* states
of the aromatic system of the carboxylate and the NO2 group.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 48–54, January–February, 2007. 相似文献
6.
The question of whether the linear absorption spectra of metal clusters can be interpreted as density oscillations (collective
“plasmons”) or can only be understood as transitions between distinct molecular states is still a matter of debate for clusters
with only a few electrons. We calculate the photo-absorption spectra of Na2 and Na5
+ comparing two different methods: quantum fluid dynamics and time-dependent density functional theory. The changes in the
electronic structure associated with particular excitations are visualized in “snapshots” via transition densities. Our analysis
shows that even for the smallest clusters, the observed excitations can be interpreted as intuitively understandable density
oscillations. For Na5
+, the importance of self-interaction corrections to the adiabatic local density approximation is demonstrated.
Received: 1 July 2001 / Published online: 10 October 2001 相似文献
7.
The calculated rate of events in some of the existing solar neutrino detectors is directly proportional to the rate of the
7Be(p, γ)8B reaction measured in the laboratory at low energies. However, the low-energy cross sections of this reaction are quite uncertain
as various measurements differ from each other by 30–40%. The Coulomb dissociation process which reverses the radiative capture
by the dissociation of 8B in the Coulomb field of a target, provides an alternate way of accessing this reaction. While this method has several advantages
(like large breakup cross sections and flexibility in the kinematics), the difficulties arise from the possible interference
by the nuclear interactions, uncertainties in the contributions of the various multipoles and the higher order effects, which
should be considered carefully. We review the progress made so far in the experimental measurements and theoretical analysis
of the breakup of 8B and discuss the current status of the low-energy cross sections (or the astrophysical S-factor) of the 7Be(p, γ)8B reaction extracted therefrom. The future directions of the experimental and theoretical investigations are also suggested.
Work supported by EPSRC, UK, grant nos J/95867 and L/94574. 相似文献
8.
Contact-like nonstandard interactions can be revealed only through deviations of observables from the standard model (SM)
predictions. We consider a number of such nonstandard scenarios, and discuss their identification as sources of deviations
in fermion-pair production processes at the international linear collider (ILC), if they were observed. We emphasize the role
of e
− and e
+ polarization in enhancing the identification reaches.
相似文献
9.
We review high-energy scattering processes that are sensitive to the hadronic structure of the photon, describing theoretical
predictions as well as recent experimental results. These processes include deep-inelastic electron-photon scattering ate
+
e
− colliders; and the production of jets, heavy quarks and isolated photons in the collision of real photons ate
+
e
− colliders, as well as in photon-photon collisions atep colliders. We also comment on minijet based calculations of totalγp andγγ cross-sections, and discuss the possibility that future lineare
+
e
− colliders might produce very large photon fluxes due to the beamstrahlung phenomenon; in the most extreme cases, we predict
more than one hadronicγγ event to occur at every bunch crossing. 相似文献
10.
L. Giuggioli Z. Kalay V. M. Kenkre 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):341-348
We study the transient dynamics of single species reaction diffusion systems whose reaction terms f(u) vary nonlinearly near
u ≈ 0, specifically as f(u) ≈ u2 and f(u) ≈ u3. We consider three cases, calculate
their traveling wave fronts and speeds analytically and solve the equations numerically with different initial conditions to study the approach to the asymptotic front shape
and speed. Observed time evolution is found to be
quite sensitive to initial conditions and to display in some cases nonmonotonic behavior, ascribable to the disparity in time
scales between the evolution of the front interior and the front tail. 相似文献
11.
L.M. Ma E. Suraud P.-G. Reinhard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(2):217-223
We discuss the properties of small metal and hydrogen clusters under irradiation by intense lasers. We use a fully non adiabatic model of coupled electrons and ions, based on density functional theory. We demonstrate the quality of such an approach in comparison to experimental data on atomic and molecular properties as well as to the optical response of small sodium clusters. We next address the response of small clusters to various lasers allowing to scan a broad span of dynamical regimes from the linear to the non linear domain. We finally discuss the impact of ionic motion in the case of hydrogen clusters irradiated by short laser pulses in the 10 13-1015 W cm-2 intensity range. 相似文献
12.
13.
F. Morales M. Monteverde M. Núñez-Regueiro 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(4):511-514
We measure electrical transport on networks of single wall nanotube of different origin as a function of temperature T, voltage V
and pressure P. We observe Luttinger liquid (LL) behavior, a conductance ∝Tα and a dynamic conductance ∝Vα. We observe a sample dependent P variation of the α parameters, interpreted as Fermi level changes due to pressure induced
charge transfer. We show how, through standard four-leads and crossed configuration methods, it is possible to determine αbulk and αend, respectively. We study and discuss the pressure and doping level dependences of the number of channels N, the LL parameter g
and the intra-rope tube-tube coupling constant U within a phenomenological model. 相似文献
14.
Density functional study of the electronic structure and properties of lithium intercalated graphite
D. Bandyopadhyay 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):643-655
Ab initio electronic-structure calculations are performed using density functional theory (DFT) with polarized basis set (LanL2DZ
and 6-311G++) within the spin polarized generalized gradient approximation for lithium intercalated graphite. Initially different benzene-Li+ model clusters are optimized on the basis of their total energy at room temperature. These model clusters are used to calculate
the optimized structure of lithium intercalated graphite clusters. The resultant optimized structures are used to calculate
dipole moment, ionization potential (IP), electron affinity (EA), binding energy (BE) and vibrational spectra (IR and Raman).
For an idea of the band gap of the clusters in the ground state, the HOMO-LUMO gap (ΔEg) has been calculated. To compare the electron transfer ability of different clusters, chemical potential (μ), hardness (η)
and their ratio for different clusters have also been determined. 相似文献
15.
We point out that the equivalent-photon approximation (EPA) for processes with massive spin-1 particles in the final state would have validity in a more restricted kinematic domain
than for processes where it is commonly applied, viz., those with spin-1/2 or spin-0 particles in the final state. We obtain
the criterion for the validity ofEPA for the two-photon production of a pair of charged, massive, point-like spin-1 particlesV
±, each of massM and with a standard magnetic moment (κ=1). In a process in which one of the photons is real and the other virtual with four-momentumq, the condition for the validity ofEPA is |q
2|≪M
2, in addition to the usual condition |q
2|≪W
2,W being theV
+
V
− invariant mass. In a process in which both photons are virtual (with four-momentaq andq′), our condition is |q
2||q′2|W
4 ≪ 16M
8, in addition to |q
2| ≪M
2, |q′2| ≪M
2 and |q
2| ≪W
2, |q′2| ≪W
2. Even when these extra conditions permitting the use ofEPA are not fulfilled, convenient approximate expressions may still be obtained assuming merely |q
2| ≪W
2 and |q′2| ≪W
2.
We also discuss how the extra conditions are altered when the vector bosons are incorporated in a spontaneously broken gauge
theory. Examples ofW boson production in Weinberg-Salam model are considered for which the condition |q
2||q′2|W
4 ≪ 16M
8 is shown to be removed. 相似文献
16.
D. Schürmann A. Di Leva L. Gialanella D. Rogalla F. Strieder N. De Cesare A. D'Onofrio G. Imbriani R. Kunz C. Lubritto A. Ordine V. Roca C. Rolfs M. Romano F. Schümann F. Terrasi H. -P. Trautvetter 《The European Physical Journal A - Hadrons and Nuclei》2005,26(2):301-305
The total cross-section of 12C(α,γ)16O was measured for the first time by a direct and ungated detection of the 16O recoils. This measurement in inverse kinematics using the recoil mass separator ERNA in combination with a windowless He
gas target allowed to collect data with high precision in the energy range E = 1.9 to 4.9 MeV. The data represent new information for the determination of the astrophysical S(E) factor. 相似文献
17.
I.M. Sokolov 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(3):369-373
We consider two-particle dispersion in a velocity field, where the relative two-point velocity scales according to v
2(r) ∝r
α and the corresponding correlation time scales as τ(r) ∝r
β, and fix α = 2/3, as typical for turbulent flows. We show that two generic types of dispersion behavior arize: For α/2 +
β < 1 the correlations in relative velocities decouple and the diffusion approximation holds. In the opposite case, α/2 +
β > 1, the relative motion is strongly correlated. The case of Kolmogorov flows corresponds to a marginal, nongeneric situation.
In this case, depending on the particular parameters of the flow, the dispersion behavior can be rather diffusive or rather
ballistic.
Received 13 March 2001 相似文献
18.
We have investigated the photoluminescence (PL) and photostimulated luminescence (PSL) spectra at 300 K to study the effect
of isoelectronic impurities K+ and I− on the formation and energy structure of Eu2+-VCs isolated dipole centers and aggregate centers in the form of single crystals of CsEuBr3 in CsBr:Eu2+ single crystals. We have shown that K+ and I− impurities in a concentration of 5 mol% do not have a substantial effect on the energy spectrum of isolated dipole centers
in CsBr:Eu2+ single crystals and the processes for the formation of such centers during growth of CsBr:Eu single crystals from the melt
by the Bridgman method. We have established that in Cs0.95K0.05Br:Eu2+, more favorable conditions are realized for the formation of aggregate centers than in CsBr:Eu2+ and CsBr0.95K0.05Br:Eu2+ single crystals. So in order to improve the storage properties of phosphors based on CsBr:Eu2+, in particular for increasing the efficiency of PSL excitation, it is expedient to dope them with K+ impurity in a concentration up to 5 mol%.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 627–630, September–October, 2007. 相似文献
19.
S. E. Bogushevich 《Journal of Applied Spectroscopy》2006,73(4):529-535
We have used EPR to study the effect of γ radiation on calcium sulfite. We have observed and identified the radiation-induced
radical ions SO
2
−
(iso) with g = 2.0055 and SO
2
−
(orth-1) with g1 = 2.0093, g2 = 2.0051, g3 = 2.0020, identical to the initial and thermally induced SO
2
−
respectively, SO
3
−
(iso) with g = 2.0031 and SO
3
−
(axial) with g⊥ = 2.0040, g∥ = 2.0023, identical to mechanically induced SO
3
−
. We have established the participation of radiation-induced radical ions SO
3
−
in formation of post-radiation SO
2
−
.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 467–472, July–August, 2006. 相似文献
20.
Antiproton proton annihilation reactions allow unique access to the moduli and phases of nucleon electromagnetic form factors
in the time-like region. We present the helicity amplitudes for the unequal-mass single-photon reaction pˉ → l
+
l
- in the s channel including the lepton mass. The relative signs of these amplitudes are determined using simple invariance properties.
Helicity amplitudes for one-photon exchange annihilation reaction pˉ → Bˉ are also given, where B is any spin-one-half particle with structure. Crossing relations between the ep → ep scattering and the pˉ → l
+
l
- annihilation channels are discussed and the crossing matrix for the helicity amplitudes is given. This matrix may be used
to verify known expressions for the space-like helicity amplitudes due to one-photon exchange. 相似文献