高电荷态Ar^q＋与Ne碰撞中入射离子电荷交换截面的研究

报道Ar^q Ne(q=8，9，11，12)碰撞体系中多电子转移过程，得到了多组实验测量电荷交换截面数据，讨论入射离子电荷交换截面、反冲离子产生截面与入射离子电荷态、能量以及散射离子电荷态的关系，并且将实验结果与Ar^q Ar碰撞体系进行对比研究。在修正分子库仑过垒模型的基础上，对实验现象做了合理的解释。     

Vlasov-kinetic computer simulations of electrostatic waves in dusty plasmas: an overview of recent results

We have performed calculations for collisions between fully stripped ions, C⁶⁺ and N⁷⁺, and atomic hydrogen, in both its ground and first excited energy levels. We have employed the Classical Trajectory Monte Carlo method to obtain total ionization and charge exchange cross sections and state selective charge exchange cross sections in the 5–500 keV/amu energy range.     

Charge exchange in collisions between heavy low-charged ions

The probabilities and the effective cross sections of collision-induced one-electron charge exchange between singly charged and four-charged heavy Xe, Cs, Ba, Pb, Bi, and U ions at energies E>0.1 keV/u are calculated by a method of multichannel normalization in the impact parameter representation. The cross sections are rather large with a maximum σ_m≈10⁻¹⁵ cm² at relative energies E _m ≈10–30 keV/u. For collision energies E<10 keV/u, the cross sections sharply decrease with growing resonance defect of the reaction. At high energies E>1 MeV/u, the charge exchange proceeds largely by the capture of inner shell electrons of the ionic targets. The charge exchange cross sections calculated for low-charged Xe, Cs, Ba, Pb, Bi, and U ions are compared with available theoretical and experimental data.     

低能高电荷态氩离子与氩原子碰撞反应截面研究

使用位置灵敏技术和飞行时间方法研究了低能高电荷态氩离子与氩原子的碰撞反应,给出了实验测量得到的入射离子电荷交换截面和转移电荷截面,研究了反应截面与不同电荷态参教的关系,并与修正后的分子过垒模型计算结果进行了比较。     

反质子与核的电荷交换反应和非弹性散射

在扭曲波冲量近似下,讨论了反质子与核的电荷交换反应A(p,n)B和非弹性散射A(p,p′)*A.并具体地计算能量为E_p=179.7MeV和46.8MeV下¹²C(p,n)¹²B,¹⁸O(p,n)¹⁸N和¹⁸O(p,p′)¹⁸O的微分截面.用严格的分波法处理扭曲波.非弹性散射的微分截面能符合实验.同时预示了在这些能量下,反质子与核发生电荷交换反应可能出现的微分截面理论结果.     

Sum rules for forward elastic pion-nucleon scattering

A number of energy weighted sum rules relating amplitudes and differential cross sections for forward elastic and charge exchange scattering to the total pion-nucleon cross section are derived from dispersion relations.     

Resonant charge exchange with the p-electron transition

The asymptotic resonant charge exchange theory is developed for slow collisions of atoms and ions with valent p-electrons. Because of a small rotation angle of the molecular axis in the course of the p-electron transition, the resonant charge exchange cross section is not sensitive to the rotational energy of colliding particles, and the cross sections are nearly equal for cases “a”, “b”, and “d” of the Hund coupling, and also for cases “c” and “e” of the Hund coupling. The cross sections of the resonant charge exchange process are evaluated under various conditions and for various elements of the periodical table with p-electron shells of atoms and ions.     

Total cross section measurements for charge exchange of He++ ions with He and Ar atoms

Total charge exchange cross sections were measured for He⁺⁺ in He and Ar gas in the energy range from 50 to 540 eV using a single beam apparatus. For He⁺⁺ in He the measured cross section is in agreement with calculations for symmetric resonant charge exchange. For He⁺⁺ in Ar the cross section for charge exchange decreases with decreasing energy below 300 eV. The measured cross section suggests the formation of Ar⁺ ions to be more important at lower energies and the production of Ar⁺⁺ to be dominant at higher energies.     

Charge distributions of many particle final states and the energy dependence of forward charge exchange

We will describe a possible dynamical origin of the energy dependence of charge exchange cross sections. Our main assumption is local compensation of charge in a certain class of many particle final states.     

Effect of the target density on the cross section of charge exchange between fast ions and atoms

When fast X^q+ X^{q^ + } ions collide with atomic or molecular targets, the total charge exchange cross section decreases with increasing target density. This is because the excitation levels of resulting X^{(q - 1)+} X^{(q - 1)^ + } ions are suppressed because of ionization by target atoms. The effect of target density on the total charge exchange cross section may amount to one order of magnitude or more depending on the charge and energy of an incident ion, as well as on the density and inner shell configuration of target atoms. Numerical calculations are performed for partial (in the principal quantum number n) cross sections σ(n) and total cross sections σ_tot=Σ_nσ(n) of charge exchange in the case of collisions of fast multiply charged ions having an energy E in the range 100 keV/u-10 MeV/u with gas or solid targets.     

Methods of estimation of equilibrium charge distribution of ions in solid and gaseous media

The new version of theoretical estimation of equilibrium charge distribution of ions passing through the matter is proposed. This estimation is based on the correction of charge exchange cross sections for gases taking into account the density effect. The results of calculations are compared with experimental data and with empirical estimation based on the averaging of experimental data for charge distributions of ions in gases and solids. The theoretical method describes the experimental oscillations of width of the charge distribution in contrast to the empirical method.     

Ionization and electron capture in neon K vacancy production from NNe collisions

Our measurements of Ne K and N K X-ray cross sections for N^{3+,4+,5+,6+,7+,} ions incident on a thin Ne target at energies from 9 to 54 MeV indicate that charge exchange plays a minor role compared to ionization in producing Ne K vacancies over that energy range.     

中高能28Si碎裂截面研究进展

介绍了利用CR-39探测器对28Si与不同靶作用的电荷变化总截面和分截面的研究进展,给出723AMeV 28Si与碳靶作用电荷变化总截面和分截面的最新实验结果。对28Si与靶核反应电荷变化总截面和分截面与束流能量和靶核质量的关系进行了讨论,发现束流能量大于200 AMeV时,中高能28Si与不同靶核反应电荷变化总截面与束流能量无关,分截面表现出明显的奇偶效应,且随靶核质量数的增加而增加。In this paper, the development of the total and partial charge changing cross sections of 28Si ions beam in different targets using the CR-39 detectors are reviewed. The newest experimental results of the total and partial charge changing cross sections of 28Si in carbon target at 723 AMeV are presented. The dependence of the target mass and the cross sections of 28Si including the total and the partial charge changing cross sections are discussed. It is found that the total charge changing cross sections of 28Si are independent of the energy when the energy of the ions beam is greater than 200 AMeV. The partial charge changing cross sections show an obviously odd-even effect, and increase with the increasing of the mass number of the target.     

Coupled-channels calculations of intermediate energy π−C inelastic scattering and charge exchange

Coupled-channels calculations have been carried out for pion inelastic scattering and charge exchange on 1p-shell nuclei at pion energies between 120 and 226 MeV. A momentum space technique is used, with the 1p-shell shell-model wavefunctions of Cohen and Kurath. Results are presented here for A=13. Channel-coupling effects are negligible in the strong 3/2^- and 5/2^- inelastic excitations of ¹³C, but enhance the analog charge-exchange cross sections by 7 to 20%.     

Study of the (p,np̃) reaction on the isotopes of tin

The cross sections for the (p, np?) reaction, where the isobaric analogue state excited in the (p, n) charge exchange reaction decays by proton (p?) emission, have been measured for the ten stable isotopes of tin. These cross sections show effects due to the neutron decay channel, decay kinematics, and the nuclear structure of the target ground state.     

Neutron-proton charge exchange scattering between 190 MeV and 590 MeV

Differential cross sections of the np charge exchange scattering between 190 MeV and 590 MeV have been measured by detecting the scattered protons in an angular range of 0^° θ_lab 18^°. The cross section at 0^° as well as the logarithmic slope of the angular distribution are found to be almost energy independent, in contrast to previous experiments, but in agreement with recent LAMPF data.     

Electron terms and resonant charge exchange involving oxygen atoms and ions

The electron terms are constructed for oxygen dimer ions at large ion-atom distances taking into account a certain scheme of summation of electron momenta on the basis of a hierarchy of various ion-atom interactions. Because the number of interaction types exceeds that in the Hund scheme, a realistic hierarchy of interactions and corresponding quantum numbers of the diatomic ion are outside the Hund coupling scheme. Electron terms are evaluated for the oxygen dimer ion in the case where the ground and first excited states of an atom and an ion belong to the respective valence electron shells p⁴ and p³ and correspond to the range of separations that determine the cross sections of resonant charge exchange in plasma. These electron terms allow us to calculate the partial and average cross sections for resonant charge exchange involving an oxygen ion and atom in the ground and first excited states in the range of collision energies of interest for oxygen plasmas. The specific features of electron terms of the oxygen ion dimer and the cross section of electron transfer are analyzed.     

Proton impact charge exchange and excitation cross sections for liquid Sn divertor studies

The quantum dynamics of charge exchange (electron capture) and excitation processes in proton collisions with Sn atoms is studied for the first time by using the two-centre atomic orbital close coupling method. The expansion basis includes the lowest nine states of singlet and triplet symmetry of Sn and all the states with n ≤ 8 of the H atom. The spin-resolved state-selective charge exchange (up to n = 5) and excitation cross sections are calculated in the energy range of 0.5 − 100 keV . Strong coupling between the electron capture and excitation channels is observed in the low-energy (E ≤ 10 keV) region associated with the energy quasi-resonance of some projectile and target states. The intensities of some strong Sn spectral lines are also calculated for a number of typical tokamak edge plasma temperatures.     

A new determination of the πN coupling constantf 2

The coupling constantf ² has been determined from forward dispersion relations for theπN helicity flip and no-flip amplitudes, using the recent information on total cross sections, phase shifts and charge exchange forward cross sections. The calculation gives also the values of the amplitudes and the first derivative at the crossing symmetry point.