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.     

Production of soft X-ray emitting slow multiply charged ions: Recoil ion spectroscopy

A study of Ne L-shell vacancy production by S^～14+, Cl^～12+ ions has shown copious production of NeIINeVIII excited states with ～10^?18 cm² cross sections and recoil velocities which may permit significantly higher resolution spectroscopy than is possible with beam-foil methods.     

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.     

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.     

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.     

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.     

Simulation of the passage of multiply charged ions through crystals

The effect of charge exchange processes on the angular distributions of quasi-isotropic beams of multiply charged ions passed through oriented crystals has been numerically simulated and the recently found effects of cooling and heating of the ion beams have been interpreted.     

Simultaneous acceleration of multiply charged ions through a superconducting linac

The possibility of simultaneously accelerating particles with a range of charge-to-mass ratios ( approximately 20%) to the same energy is proposed and demonstrated for a superconducting linac. Uranium ions stripped in a foil with eight charge states have been accelerated through a portion of the ATLAS linac from 286 to 690 MeV, with 94% of the injected uranium in the accelerated beam. Emittance of the resultant beam has been measured and the energy spread was 1.3% compared to 0.4% for a single charge state. This development has immediate application to the high-intensity acceleration of heavy ions that are limited by ion-source intensities, such as the proposed Rare Isotope Accelerator Facility.     

Multi-reference configuration-interaction calculations on multiply charged ions of carbon monosulfide

The potential energy curves for neutrals and multiply charged ions of carbon monosulfide are computed with highly correlated multi-reference configuration interaction wavefunctions.The correlations of inner-shell electrons with the scalar relativistic effects are included in the present computations.The spectroscopic constants,dissociation energies,ionization energies for ground and low-lying excited states together with corresponding electronic configurations of ions are obtained,and a good agreement between the present work and existing experiments is found.No theoretical evidence is found for the adiabatically stable CSq+(q>2) ions according to the present ab initio calculations.The calculated values for 1st-6th ionization energies are 11.25,32.66,64.82,106.25,159.75,and 224.64 eV,respectively.The kinetic energy release data of fragments are provided by the present work for further experimental comparisons.     

Radiative recombination of an electron with multiply charged uranium ions

Optics and Spectroscopy - Precise relativistic calculations of the total and differential cross sections of radiative recombination of an electron with hydrogen-, helium-, and lithium-like uranium...