Oscillator strengths of Cs and Rb-like ions

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 56, No. 1, pp. 13–17, January, 1992.     

Effective stopping of relativistic,multiply charged ions

Energy losses in collisions between heavy, multiply charged ions and light atoms are considered for ion charges Z » 1 and relative collision velocities v » 1, such that Zvc, where c is the speed of light (atomic units), as well as polarization losses in the motion of heavy relativistic ions in matter. The Born approximation is inapplicable, strictly speaking, in this range of the parameters. Simple equations are obtained for the effective stopping. A comparison is made with experiment and with the calculations of other authors.Scientific Research Institute of Applied Physics, Tashkent State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 115–119, October, 1995.     

Production of multiply charged xenon ions

A multiply charged ion source based on E.C.R. heating is described and abundances for xenon ions up to Xe¹³⁺ are given.     

Quantum electrodynamic theory of multiply charged ions

A Rayleigh-Schrödinger perturbation theory is constructed within quantum electrodynamics so as to calculate energy levels nad transition probabilities in multiply charged ions. The basic features of the suggested model are renormalization and its relative simplicity. Renormalization is guaranteed by the fact that all interesting quantities (energy levels, transition probabilities, and cross sections of various processes) are expressed in terms of many-electron Green's functions, whose renormalization is achieved by standard methods. To demonstrate the simplicity of the suggested method, expressions are obtained for corrections to the ground state energy of a two-electron multiply charged ion due to two-photon exchange diagrams, whose derivation by other methods is, in our opinion, quite more complicated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 43–54, August, 1990.     

Ultraviolet oscillator strengths for carbon,nitrogen and oxygen ions

Oscillator strengths were calculated for u.v. transitions in carbon, nitrogen and oxygen ions. Single and multiconfiguration numerical Hartree-Fock wavefunctions were used to represent initial and final states of the various transitions, and both dipole length and dipole velocity transition matrix elements were calculated. A careful choice of a few important configurations leads in most cases to multiconfiguration results which are in good agreement with experiment, and with other theoretical calculations.     

Neutralization of multiply charged ions at a surface

We report on emission processes induced by particle-solid interaction involving ions with a large potential (i.e., high ion charge state) and low kinetic energy. After an introduction into existing neutralization models for ion scattering at a metal surface a detailed discussion on the electron emission processes is presented.The number of electrons emitted per incident ion is shown to be proportional to the potential energy only within a restricted parameter field involving charge state and ion velocity. The kinetic energy distribution of emitted electrons is dominated by low-energetic electrons (30 eV), while inner shell holes of the projectile ion can initiate high-energetic characteristic Auger electrons. The presence of inner shell holes is also of importance for the charge state of highly charged ions being scattered at surfaces whereas normally the charge state distribution of scattered ions depends on the impact parameter only.The influence of the primary ion charge state on the sputtering yield of insulating surfaces is seen for the charge state of sputtered particles, whereas the total sputtering yield seems to be insensitive. This question is still subject to controversy, however.Photon emission dependent on the charge state of the impinging ion has been observed up to now only for extremely highly charged ions as hydrogenlike Ar or Kr.     

Energy loss of relativistic, multiply charged ions in an electron plasma

A simple equation is derived for calculating the energy loss of a relativistic, multiply charged ion moving in an electron plasma in the region where the Born approximation fails. The contribution of the energy losses from collisions with solitary electrons is calculated using the exact Dirac equation for relativistic Coulomb scattering. Zh. Tekh. Fiz. 68, 9–12 (February 1998)     

类Na离子振子强度的相对论效应

 采用相对论和非相对论原子自洽场方法,计算了类Na离子（原子序数为11~92）的3s-np,3p-ns和3p-nd跃迁过程的激发能和光学振子强度;通过比较相对论与非相对论的结果,研究了M壳层电子的相对论效应随原子序数的变化规律。结果表明：对n=3的跃迁过程,相对论效应主要是影响激发能,对线强度(或跃迁矩阵元)的影响不重要;对于n>3的跃迁过程,相对论效应同时影响线强度和激发能,通常对线强度的影响更大。这些结果对惯性约束聚变和X射线激光研究中需要的不透明度参数计算有重要的参考意义。     

类Na离子振子强度的相对论效应

采用相对论和非相对论原子自洽场方法,计算了类Na离子（原子序数为11~92）的3s-np,3p-ns和3p-nd跃迁过程的激发能和光学振子强度;通过比较相对论与非相对论的结果,研究了M壳层电子的相对论效应随原子序数的变化规律。结果表明：对n=3的跃迁过程,相对论效应主要是影响激发能,对线强度(或跃迁矩阵元)的影响不重要;对于n>3的跃迁过程,相对论效应同时影响线强度和激发能,通常对线强度的影响更大。这些结果对惯性约束聚变和X射线激光研究中需要的不透明度参数计算有重要的参考意义。     

Short-pulse ECR: A source of multiply charged ions

Extensive investigation is now under way in CERN (European Organization for Nuclear Research) in the framework of the Beta Beam project with the aim of gaining insight into neutrino oscillations. It is suggested that the decay of ⁶He nuclei produce neutrino beams accelerated to an energy on the order of 100 GeV/nucleon. To this end, it is necessary to generate short-pulse (30–100 μs) beams of multiply charged ions of this isotope. Conventional ECR-based ion sources seem to be inappropriate for this purpose, since the plasma density grows slowly (for more than a millisecond) in this case compared with the desired pulse duration. A design concept of a short-pulse ECR-based source of multiply charged ions is proposed. In experiments with pumping at frequencies of 37.5 and 75.0 GHz, pulses as short as ∼50 μs were obtained. Good agreement between theory and experiments is demonstrated.     

Calculation of spectral and Rosseland paths in a plasma with multiply charged ions based on a statistical approach

The semiclassical approach to determine the Fourier components of the electron dipole moment disregarding polarization (noninteracting electron model) is used for analyzing ion oscillator strengths and determining the radiation properties of plasmas consisting of multiply charged ions of heavy elements. The oscillator strength distribution df/d?? (proportional to the photoabsorption cross section) is calculated as a function of the degree of ionization and self-similar frequency ?? = ??/Z. It is found that for low degrees of ionization, function df/d?? for an ion is close to function df/d?? for a neutral atom; upon an increase in the degree of ionization, regions are formed in which df/d?? = 0 (transparency windows) and the photoabsorption cross section for high degrees of ionization differs from zero only in small frequency ranges. The resultant distribution of the ion oscillator strengths is used for calculating the polarizability of ions as a function of frequency and the cross section of radiation scattering on ions. For a gold plasma, the absorbance and opacity (both spectral and averaged according to Rosseland and Planck) are calculated. The results of computing the paths and absorption coefficients coincide in order of magnitude with the available data. The effect of scattering on the Rosseland path is estimated.     

Three-electron auger process from beam-foil excited multiply charged ions

Electron emission from collisions of C3+ ions (22.7 A MeV) with carbon foils (21, 49 and 90 microg/cm(2)) was studied by the time-of-flight method. Two prominent emission patterns can be readily identified as "binary encounter" electrons and "cusp" electrons. With the thinnest target only, a third structure is visible at slightly lower time-of-flight (thus slightly higher energy) than the cusp electrons. The energy of these electrons would correspond to 647(+116)/(-104) eV if they were emitted from the projectile frame of reference. A possible explanation is a rare three-electron-Auger K(2)L(2)L(1) process.