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1.
Investigation of transfer ionization in collisions of partially stripped carbon ions with helium at low to intermediate velocities 下载免费PDF全文
The ratios of transfer ionization (TI) to single-electron
capture (SC) cross sections have been measured for the
collisions of partially stripped Cq+ ions (q=1--4) with
He. The collision velocity ranges from 0.7 to 4.4v0
(v0 is the Bohr velocity). The projectile-ion and
recoil-ion coincidence technique is used to separate the
processes of TI and SC. The ratios reach the maximum when the
velocity is about 3.7v0 This can be explained
qualitatively based on the two-step mechanism. The experimental
results are also compared with the results calculated using the
classical trajectory Monte Carlo (CTMC) method. The CTMC results
are in agreement with the experimental data basically. The
discrepancies in higher velocity region are interpreted by the
effective charge effect. 相似文献
2.
H.J.L. van der Valk 《Solid State Communications》1976,20(8):815-818
In this paper an explanation is given of the observed large anisotropy of the static dielectric constant of 2HPbI2 (?0\t] = 26.4; ?0| = 8.7). The optical modes of 2HPbI2 are analysed in terms of long range Coulomb interactions. The results demonstrate the rather ionic nature of this compound. The polarizabilities of the I? and the Pb2+ ions obtained from the optical data are 7.2 and 4.0 × 10?24 cm3, respectively. The (Szigeti) effective charge is about 70% of the ionic charge. The anisotropy of the optical modes is caused mainly by static dipoles induced in the iodine ions by the anisotropic charge distribution in the crystal. 相似文献
3.
Electron-loss cross sections of O q+(q = 1 4) colliding with He,Ne and Ar atoms are measured in the intermediate velocity regime.The ratios of the cross sections of two-electron loss to that of one-electron loss R 21 are presented.It is shown that single-channel analysis is not sufficient to explain the results,but that projectile electron loss,electron capture by the projectile and target ionization must be considered together to interpret the experimental data.The screening and antiscreening effects can account for the threshold velocity results,but cannot explain the dependence of the ratio R 21 on velocity quantitatively.In general,the effective charge of the target atom increases with velocity increasing because the high-speed projectile ion can penetrate into the inner electronic shell of target atom.Ne and Ar atoms have similar effective charges in this velocity regime,but He atoms have smaller ones at the same velocities due to its smaller nuclear charge. 相似文献
4.
M.W. Mancini A.L. de Oliveira K.M.F. Magalhãaes V.S. Bagnato L.G. Marcassa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):317-322
In an experimental study, the multi-ionisation of metallic clusters (Nan) has been analysed in collisions with light ions in low charge states (H+, He+, He2+, O3+) at collision velocities below 1 a.u. Cluster ions are produced in charge states up to 5+. The average charge of the nano-particles
is found to increase linearly with the variation of projectile velocity and the square of the effective projectile charge,
well in agreement with the electronic stopping power of the bulk material. A fraction of 50% to 30% of the total projectile
energy loss (decreasing with velocity) is transferred into vibrational modes in good agreement with recent theoretical predictions.
Received 8 November 2000 and Received in final form 26 January 2001 相似文献
5.
6.
在中能区测量了Cq+(q=1-4)与He,Ne,Ar气体原子碰撞的电子损失截面,计算分析了入射离子损失两个电子与一个电子的总截面比 R21. 单反应道分析无法完全解释所有实验结果,必须同时考虑入射离子的电子损失、电子俘获和靶原子电离各种出射道间的耦合作用. 对于不同靶原子的碰撞,入射离子损失一个电子和两个电子的速度阈值可以由屏蔽和反屏蔽理论解释. 然而,该理论不能完全解释截面比 R21
关键词:
离子-原子碰撞
截面
电子损失 相似文献
7.
I. S. Dmitriev Ya. A. Teplova Yu. A. Belkova N. V. Novikov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2008,2(2):270-273
Based on experimental data on the ion charge distributions, the cross sections of single electron loss σ i, i + 1 and single electron capture σ i, i ? 1 by carbon ions with velocities (2.7–8) × 108 cm/s in different gaseous media (He, N2, and Ar) have been obtained. Regularities of the cross section variation of the electron capture and loss by carbon ions as a function of the ion velocity, ion charge, and atomic number of the target have been for the first time studied in a wide range of the initial ion charge, from i = 0 to i = 6. A qualitative agreement of the obtained results with the published data has been established for a number of other ions. Theoretical calculations of the cross sections of single electron loss by carbon ions in helium have been carried out. 相似文献
8.
G. J. Kumbartzki K. Hagemeyer W. Knauer G. Krösing R. Kuhnen V. Mertens K. -H. Speidel J. Gerber W. Nagel 《Hyperfine Interactions》1979,7(1):253-264
PAC measurements on the 4.43 MeV12C(2+) state on recoil in magnetized iron at velocitiesv
ion=2.1v
0, 6.0v
0, 7.4v
0 yield integral precession angles of =+0.72(18), +0.94(16) and +0.71(18) mrad, respectively. The results supplementary to existing precession data are interpreted by a distribution of C5+ ions implying a K-shell polarization of 28% and an effective charge larger than measured after emergence from the solid. The low-velocity precession tends to disagree with the empirical law of linear relationship between transient field and ion velocity. The presence of molecular orbital effects is discussed. 相似文献
9.
G.F. Liu 《Surface science》2006,600(11):2293-2298
The fraction of low energy Na+ ions neutralized during single scattering from CeO2(1 0 0) surfaces was measured with time-of-flight spectroscopy. The projectile ionization level is resonant with the surface electronic states, so that the neutralization results from a non-adiabatic charge exchange process that depends on the exit velocity and the local electrostatic potential (LEP) along the exit trajectory at a point close to the surface. Variations of the measured neutral fraction with ion energy and exit angle differ from the results obtained from clean metals due to the inhomogeneity of the LEP on an oxide surface. The results suggest that neutral fraction data collected as a function of emission angle and ion energy could be used to quantitatively map the shape of an inhomogeneous LEP. 相似文献
10.
V. I. Ritus 《Journal of Experimental and Theoretical Physics》2006,102(4):582-602
The symmetry manifests itself in exact relations between the Bogoliubov coefficients for processes induced by an accelerated
point mirror in 1 + 1 dimensional space and the current (charge) densities for the processes caused by an accelerated point
charge in 3 + 1 dimensional space. The spectra of pairs of Bose (Fermi) massless quanta emitted by the mirror coincide with
the spectra of photons (scalar quanta) emitted by the electric (scalar) charge up to the factor e
2/ħc. The integral relation between the propagator of a pair of oppositely directed massless particles in 1 + 1 dimensional space
and the propagator of a single particle in 3 + 1 dimensional space leads to the equality of the vacuum-vacuum amplitudes for
the charge and the mirror if the mean number of created particles is small and the charge e = √ħc. Due to the symmetry, the mass shifts of electric and scalar charges (the sources of Bose fields with spin 1 and 0 in 3 +
1 dimensional space) for the trajectories with a subluminal relative velocity β12 of the ends and the maximum proper acceleration w
0 are expressed in terms of the heat capacity (or energy) spectral densities of Bose and Fermi gases of massless particles
with the temperature w
0/2π in 1 + 1 dimensional space. Thus, the acceleration excites 1-dimensional oscillation in the proper field of a charge,
and the energy of oscillation is partly deexcited in the form of real quanta and partly remains in the field. As a result,
the mass shift of an accelerated electric charge is nonzero and negative, while that of a scalar charge is zero. The symmetry
is extended to the mirror and charge interactions with the fields carrying spacelike momenta and defining the Bogoliubov coefficients
αB,F. The traces trαB,F, which describe the vector and scalar interactions of the accelerated mirror with a uniformly moving detector, were found
in analytic form for two mirror trajectories with subluminal velocities of the ends. The symmetry predicts one and the same
value e
0
= √ħc for the electric and scalar charges in 3 + 1 dimensional space. Arguments are adduced in favor of the conclusion that this
value and the corresponding value α0 = 1/4π of the fine structure constant are the bare, nonrenormalized values.
The text was submitted by the author in English. 相似文献
11.
Yu. A. Belkova Ya. A. Teplova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2014,8(2):201-205
The dependences between the energy losses of beryllium ions penetrating through thin organic (celluloid) films and the initial ion charge i 0 and target thickness t are calculated. The proposed modified method is used to determine the charge fractions and average charge of an ion beam and the half-width and skewness of the charge distributions before the attainment of charge equilibrium. Calculations are performed for Be i+ ions with a velocity of 8 × 108 cm/s (E = 0.33 MeV/nucleon). 相似文献
12.
The purpose of this work is to study the adsorption of H2S from gas streams containing He and CH4 with an emphasis on the influence of the sorbent morphology on the process of adsorption. As an example of the approach, a unique modified nano-ZnO sample with a Rod-like morphology was fabricated and comparatively studied together with a nano-spherical ZnO sample under various conditions. The objective was accomplished applying central composite design (CCD) in order to screen the effects of significant adsorption parameters obtained by Placket-Burman design. Morphology of the sorbent, temperature, space velocity and H2S feed concentration were initially evaluated. Placket-Burman design experiments showed a wide deviation of adsorption capacity of 0.03-0.24 g H2S/g ZnO. Results indicated that comparing other parameters Rod like morphology comparing spherical, had significant effect on all four independent H2S adsorption parameters. Besides that, space velocity and H2S feed concentration were found to be effective parameters on adsorption of hydrogen sulfide in the range of 4000-8000 h−1 and 0.5-1 mol% respectively. Moreover, experiments revealed a negligible effect of adsorption temperature in range of 150-250 °C. The optimized condition obtained a dynamic capacity of 0.2401 g H2S/g ZnO at space velocity 4000 h−1 and H2S feed concentration of 1 mol%. Proceeding our study by significant parameters, analysis of variance (ANOVA) displayed a high coefficient of determination (R2) value of 0.931-0.959, indicating the satisfactory adjustment of the quadratic model. 相似文献
13.
A. B. Voitkiv 《Technical Physics》1998,43(3):265-270
Expressions for the cross sections for single and double ionization of atomic helium in collisions with fast multiply charged
ions are obtained in the collision parameter range υ
2≫Z≳υ, υ
0<c, where Z and υ are, respectively, the ion charge and ion velocity, υ
0 is the characteristic velocity of electrons in the atomic helium ground state, and c is the velocity of light.
Zh. Tekh. Fiz. 68, 1–7 (March 1998) 相似文献
14.
Satoshi Tsutsui Susumu Shimomura Yoshitaka Yoda Hisao Kobayashi Hideya Onodera 《Hyperfine Interactions》2014,226(1-3):637-642
149Sm nuclear resonant inelastic scattering was carried out in a charge density wave compound SmNiC2. We have investigated temperature dependences of the Sm partial phonon density of states and recoil-free fraction at the Sm site and the average sound velocity estimated from the Sm partial density of states. The Sm partial density of states exhibits temperature dependence, suggesting that the phonon modes between 20 and 25 meV may correlate with the charge density wave. Temperature dependence of the recoil-free fraction is difficult to prove the correlation with either the charge density wave or ferromagnetic ordering. The average sound velocity obtained by the Sm partial phonon density of states exhibits temperature dependence, agreeing qualitatively with very recent elastic constant measurements. 相似文献
15.
16.
A relation between quantities that characterize the breaking of the charge symmetry of nuclear forces in systems of two and three nucleons is found on the basis of an analysis of the binding-energy difference between the 3H and 3He mirror nuclei. For the neutron-neutron scattering length and effective range, the values of a nn = ?18.38(55) fm and r nn = 2.84(4) fm, respectively, were obtained by using purely nuclear parameters of proton-proton scattering in the 1 S 0 state. The calculated values agree with present-day experimental results. 相似文献
17.
K. -H. Speidel J. Cub U. Reuter F. Passek H. -J. Wollersheim N. Martin P. Egelhof H. Emling W. Henning R. S. Simon R. Schmidt H. -J. Simonis N. Gollwitzer 《Zeitschrift für Physik A Hadrons and Nuclei》1991,339(2):265-268
It is shown that transient magnetic fields in Gd-host for20Ne ions at a mean velocity of 12.5v0(v0=c/137), considerably beyond the Bohr velocity of 1s electrons of Ne ions (v1s=10v0), are dominated by the Fermi contact field of these electrons. The first excited 2+-state of2Ne was used as probe. The derived value for the mean degree of polarization p1s=0.32(13), is surprisingly large, though still consistent with values obtained at lower velocities. Present calculations of spin exchange cross sections severely underestimate the observed polarization at this high velocity.The authors are grateful to the operating staff of the UNILAC for providing excellent beam conditions. They also thank Dr. P. Maier-Komor for preparing the delicate targets. Support by the BMFT is acknowledged. 相似文献
18.
19.
Gloria Subías Joaquín García Javier Blasco Javier Herrero‐Martín M. Concepción Sánchez Julia Orna Luis Morellón 《Journal of synchrotron radiation》2012,19(2):159-173
The pattern of charge modulations and local anisotropies below the Verwey transition has been determined and quantified in high‐quality Fe3O4 single crystals and thin films grown on MgO by using resonant X‐ray scattering at the Fe K‐edge. The energy, polarization and azimuthal angle dependencies of an extensive set of reflections with potential sensitivity to charge or local anisotropy orderings have been analyzed to explore their origins. A charge disproportion on octahedral B sites of 0.20 ± 0.05 e? with [0 0 1] and cubic periodicities has been confirmed, while no significant charge disproportion has been obtained with [0 0 1/2] cubic periodicity. Additional charge modulations in the monoclinic a–b plane are also present. In addition, the occurrence of new forbidden (1, 1, 0) and (0, 0, 2n + 1/2) cubic reflections that arise from the anisotropy of the local structure around different tetrahedral and octahedral Fe atoms is shown. This complex pattern of weak charge modulations and local anisotropies is fully compatible with the low‐temperature crystal structure refined in the non‐polar C2/c space group and disproves any bimodal charge disproportion of the octahedral Fe atoms. 相似文献
20.
R. Julin J. Kantele M. Luontama A. Passoja P. Kleinheinz J. Blomqvist 《Physics letters. [Part B]》1980,94(2):123-126
The existence of the 02+ state in 146Gd at 2165.0 (4) keV is established through observation of the E0(02+ → 01+ transition. The measured half-time 375 (40) ps of this state corresponds to a monopole strength of ?2 = 0.0122 (13) which is taken as evidence against a strong state dependence of the effective proton monopole charge. 相似文献