X-ray emission of hollow atoms formed by highly charged argon and xenon ions below a beryllium surface

The X-ray emission induced by highly charged argon and xenon ions impinging on a beryllium surface is investigated. It is found that spectra of the X-ray induced by Ar-17,Ar-18+ interacting with the surface are very different from those of the X-ray induced by Ar-17,Ar-18+ interacting with residual gases. The result provides an experimental evidence for the existence of hollow atoms below the surface. Several unexpected X-ray lines are also found in the experiment. Firstly, K X-rays are observed when Ar16+ ions which initially have no K shell holes interact with the surface. Secondly, if there are more than 2 M shell vacancies at the initial time, strong M alpha alpha two-electron-one-photon (TEOP) transitions are found in the collisions of Xe-28+,Xe-29+,Xe-30+ ions with the surface.

X-ray emission produced by interaction of highly ionized Arq+ ions with metallic targets

This paper studies the X-ray spectra produced by the interaction of highly charged ions of Arq+ (q = 16, 17, 18) with metallic surface of Be, Al, Ni, Mo and Au respectively. The experimental results show that the K alpha X-ray emerges from under the surface of solid in the interaction of ions with targets. The multi-electron excitation occurred in the process neutralization of the Ar16+ in electronic configuration of 1s(2) in metallic surfaces, which produces vacancy in the K shell. Electron from high n state transition to K vacancy gives off X-ray. We find that there is no obvious relation between the shape of X-ray spectra and the different targets. The X-ray yield of incident ions are associated with initial electronic configuration. The X-ray yield of target is related to the kinetic energy of the incident ions.

Electron emission induced by the interaction of highly charged ions Pb-207(q+) (24 <= q <= 36) with solid surface of Si(110)

The electron emission induced by highly charged ions Pb-207(q+) (24 <= q <= 36) interacting with Si(110) surface is reported. The result shows that the electron emission yield Y has a strong dependence on the projectile charge state q, incidence angle psi and impact energy E. In fitting the experimental data we found a nearly 1/tan psi dependence of Y. Theoretical analysis shows that these processes are closely related to the process of potential electron emission based on the classical over-the-barrier model.

Photon emission from a chemically non-equilibrated parton gas at finite baryon density

We study hard photon production from a chemically non-equilibrated quark-gluon plasma with finite baryon density on the basis of Juttner distribution of partons of the system. We find that the photon production is ruled by early times, main contributions are given by rapidities y <= 6, and photon yield is a strongly increasing function of the initial quark chemical potential. In addition, we note that contribution from bremsstrahlung and Compton process qg -> q gamma dominates.

Slow highly charged ions induced electron emission from clean Si surfaces

The electron emission yields from the interaction of slow highly charged ions (SHCI) He2+, O2+ and Ne2+ with clean Si surface are measured separately. It is found that electron emission yield gamma increases proportionally to projectile kinetic energy E-p/M-p, ranging from 0.75 keV/u to 10.5 keV/u (i.e. 3.8 x 10(5) m/s <= v(p) <= 1.42 x 10(6) m/s), and it is higher for heavy ions (O2+ and Ne2+) than for light ion (He2+). For O2+ and Ne2+, gamma increases with Z(p) decreasing in our energy range, and it shows quite different from the result for higher projectile kinetic energy. After calculating the stopping power by using TRIM 2006, it is found that the fraction of secondary electrons induced by recoil atoms increases significantly at lower projectile energy, thereby leads to the differences in gamma for heavy ions O2+ and Ne2+ between lower and higher projectile kinetic energy.

反冲原子对低速离子轰击Si表面时电子发射产额的影响；Slow highly charged ions induced electron emission from clean Si surfaces

在兰州重离子加速器国家实验室电子回旋共振离子源高电荷态原子物理实验平台上,用低能(0.75keV/u≤EP/MP≤10.5keV/u,即3.8×105m/s≤vP≤1.42×106m/s)He2+,O2+和Ne2+离子束正入射到自清洁Si表面时二次电子发射产额的实验结果.结果表明电子发射产额γ近似正比于入射离子动能EP/MP.在相同动能下,γ(O)>γ(Ne)>γ(He),对于原子序数ZP比较大的O2+和Ne2+离子,ZP大者反而γ小,这与较高入射能量时的结果截然不同.通过计算不同入射能量下入射离子的阻止能损S,发现反冲原子对激发二次电子的作用随入射离子能量的降低显著增大,这正是导致在较低能量范围内二次电子发射产额与较高入射能量时存在差异的主要原因.

低能He~(2+)入射He原子转移电离实验中出射电子成像研究；Momentum image of emission electrons in transfer ionization process of slow He~(2+) colliding on He

利用反应显微谱仪对70keV He2+-He转移电离过程中的出射电子进行了成像,研究了出射电子的空间速度分布特征.结果表明:电子主要集中在散射平面内;在散射平面内,电子速度分布介于零与入射离子速度Vp之间(即前向出射)且在散射离子和靶核核间轴处有一极小值,呈现出典型的双峰结构.出射电子的上述分布特征可由出射电子波函数σ振幅和π振幅的干涉进行定性解释,σ振幅和π振幅对出射电子波函数的贡献与碰撞参数相关.在小碰撞参数下,π振幅的贡献更加明显;而在大碰撞参数下,σ振幅的贡献更加显著.

Probing high-density behavior of symmetry energy from pion emission in heavy-ion collisions

Within the framework of the improved isospin dependent quantum molecular dynamics (ImIQMD) model, the emission of pion in heavy-ion collisions in the region 1 A GeV as a probe of nuclear symmetry energy at supra-saturation densities is investigated systematically, in which the pion is considered to be mainly produced by the decay of resonances Delta(1232) and N*(1440). The total pion multiplicities and the pi(-)/pi(+) yields are calculated for selected Skyrme parameters SkP, SLy6. Ska and SIB, and also for the cases of different stiffness of symmetry energy with the parameter SLy6. Preliminary results compared with the measured data by the FOPI Collaboration favor a hard symmetry energy of the potential term proportional to (rho/rho(0))(gamma s) with gamma(s) = 2. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

Investigation of two-proton emission from excited states of the odd-Z nucleus P-28 by complete-kinematics measurements

An experiment to study exotic two-proton emission from excited levels of the odd-Z nucleus P-28 was performed at the National Laboratory of Heavy Ion Research-Radioactive Ion Beam Line (HIRFL-RIBLL) facility. The projectile P-28 at the energy of 46.5 MeV/u was bombarding a Au-197 target to populate the excited states via Coulomb excitation. Complete-kinematics measurements were realized by the array of silicon strip detectors and the CsI + PIN telescope. Two-proton events were selected and the relativistic-kinematics reconstruction was carried out. The spectrum of relative momentum and opening angle between two protons was deduced from Monte Carlo simulations. Experimental results show that two-proton emission from P-28 excited states less than 17.0 MeV is mainly two-body sequential emission or three-body simultaneous decay in phase space. The present simulations cannot distinguish these two decay modes. No obvious diproton emission was found.

Field emission from TiO2/Ti nanotube arrays with different morphologies

Well-aligned TiO2/Ti nanotube arrays were electrochemically formed in a HF solution for different anodization times. Field emission scanning electron microscopy (FE-SEM) images reveal that anodization time had a great influence on the morphology of TiO2/Ti nanotube arrays. The composition of resulting nanotubes was analyzed by X-ray photoelectron spectroscopy (XPS). Field emission properties of the prepared samples with different morphologies were investigated by the Fowler-Nordheim (F-N) theory. The results indicate that the morphology can affect field emission behaviors. TiO2/Ti nanotube arrays with clear, uniform, and short nanotubes display moderate field emission properties, and have the better turn-on field of 4.6 V/mu m and good field emission stability. (C) 2010 Elsevier B.V. All rights reserved.

Experimental study of the two-proton correlated emission from the excited states of Ne-17,Ne-18 and S-28,S-29

A series of experiments have been performed by complete kinematics measurements to study two-proton (2p) correlated emission from the excited states of Ne-17,Ne-18 and S-28,S-29 via the Coulomb excitation by bombarding on Au-197 target. 2p and residua coincident events were picked Out under strict conditions. Visible p-p correlations were observed. It is shown that 2p can be emitted from the high-lying excited states. 2p halo may lead to 2p emission with large spectroscopy factor for the states close to or beyond the threshold.

Unified fission model for proton emission

The unified fission model (UFM) combining with the phenomenological assault frequency has been carried out to investigate the proton-radioactivity half-lives of spherical proton emitters. The results are in good agreement with the experimental data and other theoretical values, and newly observed spherical proton emitters have been analyzed. Finally, the effect of angular momentum transfer on half-life of proton emission has been discussed in detail and a formula can be used to describe this relationship.

PROBING THE SYMMETRY ENERGY AT SUPRA-SATURATION DENSITIES FROM PION EMISSION IN HEAVY-ION COLLISIONS

Within the framework of the improved isospin dependent quantum molecular dynamics (ImIQMD) model, the emission of pion in heavy-ion collisions in the region 1 A GeV as a probe of nuclear symmetry energy at supra-saturation densities is investigated systematically, in which the pion is considered to be mainly produced by the decay of resonances Delta(1232) and N*(1440). The pi(-)/pi(+) yields are calculated for selected Skyrme parameters SkP, SLy6, Ska and SIII, and also for the cases of different stiffness of symmetry energy with the parameter SLy6. Preliminary results compared with the measured data by the FOPI collaboration favor a hard symmetry energy of the potential term proportional to (rho/rho(0))(gamma s) with gamma(s) = 2.