Inelastic processes in collisions of multicharged fast ions with atoms

We use the eikonal approximation to develop a general formula for the cross sections of inelastic collisions of multicharged fast ions (including relativistic ions) with atoms that is applicable within a broad range of collision energies, has the standard nonrelativistic limit, and becomes, in the ultrarelativistic case, the well-known result that follows from the exact solution of the Dirac equation. As an example we study the excitation and ionization of a hydrogenlike atom, the single and double excitation and ionization of a heliumlike atom, and multiple (up to the eighth order) ionization of the neon atom and (up to eighteenth order) ionization of the argon atom. We derive simple analytical expressions for the inelastic cross sections and establish recurrence relations linking the cross sections of ionization of different orders. Finally, we compare our results with the experimental data. Zh. éksp. Teor. Fiz. 114, 1646–1660 (November 1998)     

Processes of dissociative excitation in collisions of electrons with CaI<Subscript>2</Subscript> molecules

The dissociative excitation of calcium atoms and ions and calcium monoiodide in e-CaI₂ collisions was studied by the method of extended crossing beams. The excitation cross sections of calcium atoms and ions in electron-atom and electron-molecule collisions are compared. The main channels of the reactions at low electron energies are discussed.     

Excitation of a singly charged indium ion by electron impact

Inelastic collisions of slow electrons with indium atoms resulting in the production of excited singly charged indium ions are experimentally studied. Excitation cross sections of 123 InII spectral lines are measured at the excitation electron energy of 30 eV. Nine optical excitation functions are recorded. The dependence of the excitation cross sections on the principal quantum number of the upper level is examined for 12 InII spectral series.     

The dissociative excitation of doublet and sextet manganese atom levels in collisions of electrons with manganese dibromide molecules

Inelastic collisions of electrons with manganese dibromide molecules were studied by the method of extended crossing beams. These collisions cause the formation of excited manganese atoms in doublet and sextet states. At an exciting electron energy of 100 eV, 52 dissociative excitation cross sections were measured. At electron energies 0–100 eV, three optical excitation functions were recorded. The ratio between excitation cross sections in electron-molecular and electron-atomic collisions is considered.     

Binary encounter approximation for the electron-impact double ionization cross section of atoms and ions

An binary encounter approximation is formulated for the direct (without any excitation of autoionization levels) double ionization of atoms and ions by electron impacts. Analytical expressions are derived for the cross section, which qualitatively represent the main dependences on the incident electron energy and atomic parameters.     

Electron-impact excitation cross sections of gallium atom

Excitation of gallium atom in collisions with slow electrons is studied using the method of extended crossing beams with recording of the optical signal of excited atoms. At an electron energy of 30 eV, 66 excitation cross sections are measured. In the electron energy range of 0–200 eV, 24 excitation optical functions are recorded. The dependence of the cross sections on the principal quantum number of an upper level is obtained for eight spectral series of Ga I. The results obtained are compared with the data of the previous experiment.     

Scaling properties of target excitation cross sections in collisions between atoms and multiply charged ions

The scaling properties of one-electron target excitation cross sections in collisions between atoms and multiply charged ions are investigated. For the example of bare-ion (Z)-hydrogen collisions with various charge numbers Z it is shown that, in many-state calculations for Z ≥ 2 and energies E/Z ≈ 15–100 keV/amu, calculated 2p excitation cross sections lie approximately on a universal curve. This curve deviates from the one which has been derived earlier by Janev and Presnyakov for all Z on the basis of a simplified three-state model, and in fact results from a consistent three-state treatment show no scaling. The scaling properties of the excitation cross sections are easily understood in a purely classical model of distant collisions.     

Atomic excitations in sputtering studied with group two element targets

Solid targets of Be, Mg, Zn, and Cd have been bombarded with 50 keV Ar⁺ ions. The relative excitation of the lowest-lying excited levels in sputtered neutrals and singly-charged ions have been measured using optical spectrometry. It is found that singly-charged ions are excited much more efficiently than neutral atoms. This is discussed, and it is concluded that atomic excitation in sputtering results from electron pick-up to excited states in initially ionized atoms rather than from inelastic atom-atom or electron-atom collisions.     

Excitation of singlet levels of a singly charged scandium ion in e-Sc collisions

The excitation of singlet levels of the singly charged scandium ion is experimentally studied in collisions of slow electrons with scandium atoms. At the exciting electron energy of 30 eV, 59 excitation cross sections are measured. In the electron energy range of 0–200 eV, seven optical excitation functions are recorded. On the basis of these data the total excitation cross sections are calculated for 11 even and 9 odd levels of Sc II, as well as the contribution of cascade population to 8 even and 7 odd levels.     

Ne+离子与Li原子碰撞过程中激发态的研究

本文通过观测Ne⁺离子与Li原子碰撞中的发射谱,对碰撞中的电子俘获和靶激发过程进行了研究。在可见光范围给出了所观察到的各条谱线的发射截面及相应上能级的激发截面。对电子俘获过程与能量亏损和靶原了电离势的关系进行了讨论。Ne⁺离子能量范围为20—150keV 关键词：     

单、双电荷离子与原子碰撞中的激发态和发射截面比较

本文给出了单、双电荷离子和He,Ne,Ar,碰撞过程中产生的激发态的实验结果。He^q+,Ar^q+(q=1,2)离子束实验室能量为(70—170)×q keV。光学测量由光学多道分析系统(OMA)完成,波长范围为200—800nm。观察到单、双电荷离子和原子碰撞中各种不同的激发过程,讨论了发射截面和入射离子电荷数、势能亏损的依赖关系。 关键词：     

高能入射电子与原子离子碰撞激发截面

本文采用玻恩近似,计算高能入射电子与原子(离子)碰撞激发截面。其中仔细处理了包括复杂原子在内的跃迁矩阵元角部分,因而可以作广泛计算。本文还将计算所得结果与其他方法作了比较,其符合程度一般是相当好的。     

Radiation field and resonant two-center dielectronic transitions in relativistic ion-atom collisions

We consider projectile-electron excitation and loss in relativistic collisions of ionic projectiles with excited atoms. We show that under certain conditions electron transitions in the ion and atom can be resonantly coupled in the collision via the radiation field. The resonance becomes possible due to the Doppler effect, has a well-defined impact energy threshold, and clearly manifests itself in the cross sections. Since the range of the ion-atom interaction in the resonance case is very long, the presence of other atoms in the target medium as well as the size of the space occupied by the medium have to be taken into account. As a result, the cross section may become dependent on the density of the target atoms and/or the target size.     

Dissociative excitation of doublet and octet levels of the manganese atom in collisions of electrons with manganese diiodide molecules

The dissociative excitation of doublet and octet levels of the manganese atom in collisions of slow electrons with manganese diiodide molecules is studied. At the exciting electron energy of 100 eV, the excitation cross sections for 28 and 12 transitions, respectively, from doublet and octet states of manganese atom are measured. In the exciting electron energy range of 0–100 eV, six optical excitation functions are recorded. The possible channels of the formation of excited manganese atoms at low electron energies are discussed.     

_(18)Ar~(q~ )(q=3,4)与H和He碰撞的电荷剥离截面

采用二体碰撞近似和托马斯 -费米近似计算了多电荷离子18Arq ( q =3,4 )与中性原子H和He碰撞的电荷剥离截面以及Arq 的势函数和电子动量分布 ,计算结果与文献 [4]中的数据符合得较好。所导出的计算公式和编制的计算程序可以计算任何一个多电荷离子Aq 与H或He碰撞的电荷剥离截面。因而具有一定的普适性。     

Excitation of a singly charged barium ion in electron-atom collisions

Results of the experimental study of excitation of transitions of singly charged barium atoms in collisions of low-energy monokinetic electrons with barium atoms are presented. Regularities of the behavior of cross sections for excitation in spectral series of BaII are found. The results are compared with other authors’ results.     

Cross sections of inelastic processes in collisions between relativistic structured heavy ions and atoms

A nonperturbative method is developed for the calculation of cross sections of inelastic processes in collisions between structured high-charge heavy ions moving at relativistic velocities and atoms. By structure ions are meant partly stripped ions consisting of an ion nucleus and a number of bound electrons which partly compensate the core charge and form the electron “coat” of the ion. The single ionization cross section of hydrogen atom and single and double ionization cross sections of helium atom are calculated. It is demonstrated that the inclusion of the extent of ion charge may bring about a marked variation of the respective cross sections compared to ionization by point ions of the same charge and energy.     

Multiple ionization of atoms and the energy of recoil ions in collisions with fast,multiply charged ions

On the basis of the sudden perturbation approximation and the model of independent electrons, simple analytical expressions are obtained for the cross sections of multiple ionization of atoms and the average energies of recoil ions in collisions between atoms and fast, multiply charged ions in the range of parameters in which the Born approximation is inapplicable. An expression for the energy distribution function of recoil ions is also obtained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 111–116, April, 1996.     

Experimental investigation of ultracold atom-molecule collisions

Ultracold collisions between Cs atoms and Cs2 dimers in the electronic ground state are observed in an optically trapped gas of atoms and molecules. The Cs2 molecules are formed in the triplet ground state by cw photoassociation through the outer well of the 0-(g) (P3/2) excited electronic state. Inelastic atom-molecule collisions converting internal excitation into kinetic energy lead to a loss of Cs2 molecules from the dipole trap. Rate coefficients are determined for collisions involving Cs atoms in either the F=3 or F=4 hyperfine ground state, and Cs2 molecules in either highly vibrationally excited states (nu'=32-47) or in low vibrational states (nu'=4-6) of the a3 summation(u)+ triplet ground state. The rate coefficients beta approximately 10(-10) cm3/s are found to be largely independent of the vibrational and rotational excitation indicating unitary limited cross sections.     

Electron-impact excitation of even septet levels of an iron atom

Excitation of even septet levels of the iron atom by collisions with slow electrons is studied by the method of extended crossing beams. At an exciting electron energy of 50 eV, 72 excitation cross sections are measured. In the electron energy range of 0?C200 eV, 15 optical excitation functions are recorded. The obtained results are used to evaluate the total excitation cross sections of the even septet levels.