Ya. A. Teplova

Attainment of equilibrium charge distributions in fast ion beams passing through solid films

Abstract The thicknesses Ts of carbon targets needed for equilibration of the charge distribution in H, He and N ions beams have been calculated in the energy range E = (0.03–100) MeV/amu. The calculations have shown that for N ions at E = 0.1 MeV/amu the value of Ts is 20 times Tg in a gas target and that the difference decreases with increasing energy.

Database on charge – changing cross sections in ion – atom collisions

The database on charge changing cross sections in ion-atom collisions is presented. The capture and loss of one or more electron cross sections are summarized in tables and figures as a function of incident ion energy. The experimental, theoretical and recommended data are compiled.

On the target thickness to attain equilibrium charge distribution in a beam of fast ions

Abstract The equilibrium thicknesses T of H 2 , He, N 2 and Ar gastargets have been calculated for some ions with nuclear charge Z = 1–92 at energies E = 10 −2 −10 3 MeV/amu. The dependence of T on various parameters is studied. The maximum values of charge distribution halfwidth d are shown to be attainable at target thicknesses lower then equilibrium.

METASTABLE STATES OF MULTIPLY CHARGED IONS.

Abstract The lifetimes have been measured and the number of excited states for the helium-like and lithium-like particles contained in the beams of ions 9Be, 11B, 13C, 14N, 16O after passing through a thin celluloid film.

Density effects in heavy ion charge-exchange processes in gaseous and solid targets

Abstract Experimental results on the pre-equilibrium and equilibrium charge distributions in celluloid films for incident Be, B, C, N, O ions are analyzed in order to obtain charge-exchange cross-sections. The determined “effective” cross-sections of electron capture and loss in celluloid together with earlier measured analogous cross-sections in nitrogen allow us to calculate charge fractions Fi(t) depending on the target thickness in solid (celluloid) and gaseous (nitrogen) matter. The absolute values and the ratios Acap=σgi,i−1/σsi,i−1 and Aloss=σgi−1,i/σsi−1,i of electron capture and loss cross-sections in {s} solids (celluloid, carbon) and {g} gases (nitrogen) are under consideration.

Multicomponent approximation for evaluation of nonequilibrium charge fractions of ions passing through thin films

A method is proposed to calculate the nonequilibrium charge fractions and mean charges of light ions, depending on film thickness. The calculated results are presented for three charge fractions of 0.75 MeV/nucleon B ion beam, passing through the organic film, and for four charge fractions of 2 MeV/nucleon Ne beam, passing through the carbon film. The dependence of energy loss on the initial charge of projectile Ne ions and target thickness in the nonequilibrium conditions is examined.

Analysis of the relationship between the electron-capture and electron-loss cross sections for carbon ions

The electron-loss cross sections σi, i + 1 and the electron-capture cross sections σi, i − 1 for carbon ions with energies of 35–330 keV/nucleon in hydrogen and neon are determined from experimental data. It is demonstrated that, for particle energies which satisfy the condition σi, i + 1 = σi, i − 1 or σi, i − 1 = σi − 1, i, the average equilibrium ion charge can be evaluated without solving the system of differential equations for charge exchange. The dependence of the average equilibrium ion charge on the ion energy is investigated for carbon ions.

Charge distribution of nitrogen ions reflected from copper and graphite surfaces

A method for the theoretical estimation of the equilibrium charge distribution of ions passed through a media is proposed. It is based on the correction of charge-exchange cross sections for gases using a factor taking the density effect into account. The calculated charge distribution of N ions in graphite agrees well with the existing experimental data. This method makes it possible to estimate the charge distribution of fast N ions reflected from a Cu surface.

Features of the pre-equilibrium charge states of light ions passing through thin celluloid films

A semi-empirical method for establishing of the average charge of ions passing through thin celluloid films is proposed. Calculations for helium (He) and nitrogen (N) ions with different initial velocities (12−18.7 × 108 cm/s for He and 4−12 × 108 cm/s for N) are presented. The equilibrium thickness of a celluloid target in dependence on the initial charge states of incident ions is evaluated.

Oscillations of the charge exchange cross sections and the average equilibrium charge of helium ions

The electron loss and capture cross sections for helium ions at velocities nu =8-20*108 cm s-1 in helium, nitrogen, neon and argon have been measured and the electron capture cross sections for He+ and He2+ ions in various media have been theoretically calculated in the Oppenheimer-Brinkman-Kramers approximation. It has been found that the dependence of the electron capture cross section on the nuclear charge of the target atoms is oscillating. This phenomenon is caused by the analogous oscillations of the values of the equilibrium charge fraction and the average charge of the fast ions.