共查询到20条相似文献,搜索用时 15 毫秒
1.
A closed variant of the Born approximation for calculating differential scattering cross sections in ion-atom collisions is developed. An expression in terms of the matrix elements J ij with respect to the single-electron states of the atom is found for the matrix element describing the target atom in the formula for the differential cross section. The matrix elements J ij are averaged over the relative orientation of the momentum transferred in the collision and the symmetry axis of the electronic orbitals of the target atom, using the single-electron Rutaan-Hartree-Fock wave functions. The algebraic representation of the matrix elements J ij makes it possible to perform calculations for atoms with any value of Z. The model developed is used to calculate the cross sections σ Σ and characteristic scattering angles θ c for the process of electron loss by H ? ions with energy E = 0.1–100 MeV in targets consisting of atoms with Z = 2–54. It is shown that σ Σ ∝ E ?1 and θ c ∝ E ?1/2 for all Z, and for fixed E the behavior of σ Σ( Z) and θ c( Z) is determined by the order of filling of the electronic shells of the target atoms (the ionization potential). The computational results are analyzed and compared with the experimental data and the results of other calculations. 相似文献
2.
Ionization of hydrogen atom by charged particle impact are studied at different collisional energies and the total and differential
cross sections are calculated. In case of light particle impact the final-state wave function here considers all three two-body
interactions on an equal footing and satisfies the exact Coulomb boundary conditions. The spin asymmetries are also found
and the values are compared with other existing results. For heavy particle impact a final continuum state wave function which
incorporates distortion due to the Coulomb fields of both the projectile and the target nuclei is employed. In this case the
target hydrogen atom is considered in its ground as well as metastable 2 s state. The results thus obtained are compared with the existing experimental findings as well as other theoretical predictions. 相似文献
3.
Channeling problem produced by confining environment that leads to resonance scattering of charged particles via quasistationary
states imbedded in the continuum is examined. Nonmonotonic dependence of physical parameters on collision energy and/or confining
environment due to resonance transmission and total reflection effects is confirmed that can increase the rate of recombination
processes. The reduction of the model for two identical charged ions to a boundary problem is considered together with the
asymptotic behavior of the solution in the vicinity of pair-collision point and the results of R-matrix calculations. Tentative estimations of the enhancement factor and the total reflection effect are discussed.
The text was submitted by the authors in English. 相似文献
4.
We give the Lagrangian of a system of moving charged particles up to the fourth approximation in 1/ c neglecting dipole radiation of the system. In this case the appearance of the electromagnetic waves (quadrupole radiation) by moving charges occurs in the fifth approximation in 1/ c. 相似文献
5.
We report on a search for charged massive long-lived particles (CMLLPs), based on 5.2 fb(-1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron pp collider. We search for events in which one or more particles are reconstructed as muons but have speed and ionization energy loss (dE/dx) inconsistent with muons produced in beam collisions. CMLLPs are predicted in several theories of physics beyond the standard model. We exclude pair-produced long-lived gauginolike charginos below 267 GeV and Higgsino-like charginos below 217 GeV at 95% C.L., as well as long-lived scalar top quarks with mass below 285 GeV. 相似文献
8.
Electric monopole transitions between the 0 2 + , 0 1 + and 2 2 + , 2 1 + levels in 76Se, populated in the decay of 76Br, were investigated by means of conversion electrons and gammaray spectroscopy. The K-electron intensity ratios of E0 and E2 transitions connecting the 0 2 + level to the 0 1 + and 2 1 + levels and of the E0 and E2 components in the 2 2 + →2 1 + transition were determined. The ratio X( E0/ E2) of the E0 to E2 reduced transition probabilities and, from the available lifetimes, the E0 strength parameters ρ( E0) were deduced for the two transitions. The results are compared with the predictions of current models. 相似文献
9.
We rigorously prove that for compact charged general relativistic objects there is a lower bound for the mass–radius ratio.
This result follows from the same Buchdahl type inequality for charged objects, which has been extensively used for the proof
of the existence of an upper bound for the mass–radius ratio. The effect of the vacuum energy (a cosmological constant) on
the minimum mass is also taken into account. Several bounds on the total charge, mass and the vacuum energy for compact charged
objects are obtained from the study of the Ricci scalar invariants. The total energy (including the gravitational one) and
the stability of the objects with minimum mass–radius ratio is also considered, leading to a representation of the mass and
radius of the charged objects with minimum mass–radius ratio in terms of the charge and vacuum energy only. 相似文献
10.
An estimate is made of the maximum number of resonant particles interacting with a transverse plane electromagnetic wave. This estimate is based on the distribution function, in terms of integrals characterizing the motion of particles in a wave. The values found here for proton fluxes accelerated by an amplitude-modulated wave in the solar corona agree with those measured during sporadic radioemission bursts. 相似文献
11.
We have constructed magnetostatic traps from permanent magnets for trapping charged and neutral atoms. Two storage experiments
are presented: a compact Penning trap for light ions and magnetic trapping of single neutral atoms. The dynamics of cold neutral
atoms and their loss mechanisms in a quadrupole magnetostatic trap are discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
New regulations regarding the PM1 emission by power plants and transport vehicles require novel technical solutions for the abatement of particulate matter emission in submicron size range. Particles of this size are difficult to remove by conventional methods, and therefore various variants of wet electrostatic scrubbers have been developed. In such devices, the electrostatic forces between charged particles and collectors (water droplets) are used to permanently remove them from the gas. The paper focuses on the state-of-the-art of wet electrostatic scrubbing technique used for the removal of submicron particulate matter from exhaust gases with particular emphasis upon marine Diesel engines. 相似文献
13.
The electromagnetic surface polarization fields induced on the surface of a solid by moving charged particles are calculated. The case when a particle moves parallel to the surface is analyzed in detail.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 94–99, January, 1995. 相似文献
14.
Thermoluminescent detectors (TLDs) are widely used for the dosimetry of photons and electrons. They are less used for the radiation with higher linear energy transfer (LET). One of the reasons for that is that their TL relative efficiency η decreases for the most of them with increasing LET. The paper presents first a review of author's experimental results in which η was established for charged particles having LET of the order from 1 to 100 keV/μm in tissue. Among TLDs studied were known materials like LiF:Mn; Ti; Al–P glass; CaSO4:Dy; Al2O3:Na; and Al2O3:C. It was found that the dependence of their η on LET is not the same for all TLDs studied. The response of the same materials to neutrons was also studied. It was found that both η as the relative response (RR) defined in terms of absorbed dose in tissue are different, they depend critically also on the composition. When a TLD contains nuclei like 6Li and 10B, their RR would be rather high. As far as η is concerned, the same tendencies were observed as for charged particles, i.e. when average LET of secondary particles formed in a TLD increases, their η generally decreases. 相似文献
15.
The stochastic Eden model of charged particles aggregation in two-dimensional systems is presented. This model is governed
by the following two parameters: screening length of electrostatic interaction, , and short-range attraction energy, E. Different patterns of finite and infinite aggregates are observed. They are of the following morphology types: linear or
linear with bending, worm-like, DBM (dense-branching morphology), DBM with nucleus, and compact Eden-like. The transition
between the different modes of growth is studied and phase diagram of the growth structures is obtained in co-ordinates. The detailed aggregate structure analysis, including analysis of their scaling properties, is presented. The
scheme of the internal inhomogeneous structure of aggregates is proposed.
Received 2 September 1998 and Received in final form 15 January 1999 相似文献
16.
JETP Letters - Recently, in the series of works a new effect of acceleration of particles by black holes has been found. Under certain conditions, the energy in the center-of-mass system can become... 相似文献
17.
The angular and energy distribution of secondary electrons ejected in collisions of heavy charged particles has been calculated in the binary encounter approximation using the statistical Thomas-Fermi method. Comparisons are made with reported experimental results. 相似文献
18.
The recently obtained results on e +e ? → hadrons and multigamma production in pp collisions provide some support for a previously made argument that heavy, highly charged subnucleons may exist, and a search for such particles in cosmic rays has been made. In 620 hours no candidates were detected, and an upper limit for the unaccompanied particle flux of 7 · 10 ?10 cm ?2 sec ?1 sr ?1 at sea level under 600 g/cm 2 concrete is obtained with 90% confidence. 相似文献
19.
The coordinate asymptotics of eigenfunctions is investigated for a system of three particles with a Coulomb interaction. The confluent hypergeometric function is used for describing the asymptotics in some directions of configuration space. 相似文献
|