Preequilibrium emission of nucleons from reactions induced by medium-energy heavy ions

Zeitschrift für Physik A Hadrons and nuclei - The preequilibrium emission of nucleons from reactions induced by medium-energy heavy ions is analyzed by using (i) the first term of the...     

Calculation of the ranges of slow, heavy ions in an amorphous medium

The low-energy range corresponding to reduced energies ɛ⩽0.1 is investigated. A method is developed for calculating the ranges of heavy ions in an amorphous medium. Analytical expressions for calculating the projective range of ions and the standard deviation of the projective ranges are obtained. The computational results are in good agreement with experiment. Zh. Tekh. Fiz. 67, 16–20 (October 1997)     

Ranges of 0.2-1.0 GeV/nucleon heavy ions in nuclear photoemulsion

Heavy nuclei transport in matter are studied experimentally and theoretically. Our experimental range and straggling values of 0.2 – 1.0 GeV/nucleon ²⁰Ne, ⁴⁰Ar, ⁵⁶Fe, ¹⁹⁷Au and ²³⁸U nuclei in BR-2 nuclear photoemulsion are presented and compared with model calculations carried out according to our RANGE-program and the PRAL-model (version of 1987) developed by Ziegler et al. The presented data analysis points at the necessity to take into account Z³-correction in Bete-Bloch formula when ionization losses of very heavy multicharge ions (for example ¹⁹⁷Au and ²³⁸U) are calculated. The comparison of experimental and calculated results showed that RANGE program can correctly calculate the ranges and straggling of heavy ions. The difference between experimental and theoretical data do not exceed 5% in all of the cases examined. PRAL model describes the heavy ion ranges quite adequately, but overestimates the particle range straggling.     

Ranges of low-energy heavy ions in beryllium, boron, carbon, and silicon

Based on a theory of the passage of low-energy, heavy ions through matter, simple analytical expressions are obtained for calculating the average projected ranges of the ions and the rms deviations of the projected ranges. The theoretical and experimental ranges of heavy ions with atomic numbers 29⩽Z ₁⩽83 in targets of Be, B, C, and Si are compared. The theory is found to be in good agreement with experiment. Zh. Tekh. Fiz. 68, 33–36 (September 1998)     

Transient field measurements on light and heavy ions in amorphous iron-boron compounds

Measurements of transient magnetic fields (TF) were performed for the first time in the amorphous compounds of Fe₈₀B₂₀ and Fe₈₅B₁₅ for ²⁴Mg(2⁺), ²⁸Si(2⁺), ⁴⁸Ti(2⁺) and ⁵⁶Fe(2⁺) probe ions employing light and heavy ion beams. The motivation for these experiments was to investigate whether ion beam induced attenuations of TF are substantially weaker in these materials than in crystalline Fe. This expectation was indeed satisfied. The attenuations observed were found to be smaller at least by a factor of 2.     

Mössbauer study of amorphous alloys irradiated with energetic heavy ions

The Mössbauer spectroscopy was applied to study radiation damage in metal-metalloid amorphous alloys irradiated with⁴⁰Ar/E=225 MeV/ or¹³²Xe/E=120 MeV/ ions at room temperature. The observed dose dependent changes in the intensity of the Mössbauer lines and of the hyperfine field distributions can be associated with structural changes in short-range order of the irradiated amorphous alloys.     

Simulation of the relief formation a on an amorphous solid surface under bombardment by medium-energy ions using the method of statistical tests: Case of grazing ion incidence

The formation of a wave-like relief on the surface of an amorphous solid under ion bombardment at a grazing angle of incidence (87.5° from the normal to surface) has been investigated by the method of statistical tests. Collision cascades are calculated within the approximation of binary collisions. The irreversible relaxation of the Wolf-Villain type is used for surface relaxation. It is shown that a wave-like relief is formed if, along with modification of the target surface, modification of the target bulk is taken into account.     

Ranges and standard deviations of implanted ions

This paper presents a theoretical analysis and simple expressions for the calculation of ranges and standard deviations of implanted ions in amorphous targets. Nuclear energy loss models are discussed to introduce an approximation formula for the nuclear stopping cross section appropriate for Thomas-Fermi, Lenz-Jensen and intermediate type potentials. The Firsov electronic stopping model has been used to show its successful application. Algebraical expressions for the total range of ions in monoatomic and biatomic targets as a function of ion energy result from the considerations presented. A quasi-elastic multiscattering model is suggested, which permits an easy estimate of projected ion ranges. The standard range deviation is obtained by determining the total average-square energy loss fluctuations. Finally a comparison of calculated and experimental results is made to show that calculations based on the Firsov electronic stopping model and the nuclear stopping cross section proposed here provide a better agreement with the experimental results than the wellknown Johnson-Gibbons LSS-calculations.     

Ranges of light ions in materials with different densities

The ranges of He, Li, Be, B, and C ions in gases and NIKFI-Ya2 nuclear photoemulsion are considered. The general features of the range variations as functions of the energy and ion nuclear charges are discussed. The results of calculations are compared with experimental data and the data of calculations using the SRIM-2013 program.     

Range of Er ions in amorphous Si

We have measured the range and range straggling for energetic 100-900 keV Er ions in amorphous Si by means of Rutherford backscattering followed by spectrum analysis. The results are compared with other experimental data and Monte Carlo (SRIM-2003) calculations. Our experimental results show that, although the measured values for both range and range straggling exceed the SRIM predictions, they are nevertheless consistent with trends that have been previously observed. We see no anomalous trends in range and range straggling parameters for the rare earth ions for implant energies E ≥ 100 keV. We present a detailed consideration of ⁴He stopping powers in Si due to its crucial impact on RBS range measurements.     

Reflection of heavy ions

The backscattering of heavy ions from surfaces is investigated by computer simulation (TRIM.SP). The particle and energy reflection coefficients are shown to scale with the ratio of target mass to ion mass as well as with the reduced energy for >0.02 and for normal incidence. At lower energies not only the scaling breaks down but also the effect of a chemical binding influences the reflection coefficient. The calculated data include also the dependence of the reflection coefficients on the angle of incidence as well as angular and energy distributions. Simulated results are in reasonable agreement with those from analytical theory and experiment.     

Nanoisland nucleation in thermal spike regions on the material surface irradiated by swift heavy ions

The energy that is lost by swift heavy ions (SHIs) in a material highly excites its electronic subsystem, while the ion subsystem initially remains almost unperturbed. Subsequent energy transfer from the excited electrons to target atoms may cause a short-term local temperature rise (thermal spike), which, in turn, may induce phase transitions in the nanodimensional region near the ion trajectory. The possibility of nanoisland nucleation within such spikes on the material surface exposed to SHIs is studied. Presumably, the nanoislands appear when the characteristic nucleation time is shorter than the time of spike region cooling. It is shown that the maximal nucleation rate may be observed at a distance of the center of the spike. This may result in the annular distribution of the islands around the SHI trajectory.     

Formation of the charge and energy distributions of heavy ions in a material in the diffusion model

We investigate the formation of the charge and energy distributions of ions that slow down and randomly change their charges in collisions with particles of the medium. We study the influence that the spread of ions in charge has on the shape of the Bragg curve. The suggested diffusion approximation for the kinetic equation of heavy ions allows the parameters of the ion charge and energy distributions to be easily determined in the entire ion path. The parameters of the ion charge distribution are shown to be related to the ionization-recombination cross sections. The ion distributions calculated in the suggested analytical model are compared with the results of numerical calculations. We have obtained good agreement between the analytical, numerical, and experimental results.     

Experimental investigation of the energy distribution of sputtered excited target atoms bombarded by medium-energy ions

In this paper we experimentally investigate the parameter dependence of a model energy distribution of excited potassium atoms, knocked out by bombarding a KCl monocrystal with normally incident Ar⁺ ions, on the ion energy and the partial oxygen pressure in the chamber. On the basis of the obtained results a model of the energy distribution is proposed that corresponds to the kinetic formation mechanism for the excited atoms during the sputtering of the target.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 9–12, March, 1985.     

Visible spectra of heavy ions with an open 4f shell

We present visible to near-infrared spectra of highly charged Yb (the atomic number 70) and W (74) obtained with a compact electron beam ion trap. By observing the dependence on the electron beam energy, the charge state that should be assigned to the observed lines is determined. For In-like Yb²¹⁺ and W²⁵⁺ and Sn-like W²⁴⁺, the experimental spectra are compared with theoretical calculations done by the CI+all-order method. In each spectrum, the most prominent line is identified as the magnetic dipole transition from the first excited fine structure level to the ground level in the ground electronic configuration, 4f³ for In-like ions and 4f⁴ for Sn-like ions.     

Fragmentation of relativistic heavy ions

The “incoherent droplet model” is used to explain recent experiments on the fragmentation of ¹⁶O during high energy collision with a Be target. In the ¹⁶O rest frame the fragments have a universal iso tropic Gaussian momentum distribution, independent to the masses of the fragments. The half-width of the Gaussian is $\text{〈p〉 (}\text{A}\text{3}{}_{\mathrm{n}}\text{)}$, where, A is the mass number of the nucleus, n is the total number of fragments, and 〈p²〉 is the mean square momentum of individual nucleons in the fragmenting nucleus.     

Range parameters of heavy ions in amorphous targets at LSS-energies of 0.0006⩽ ϵ ⩽ 0.3

Heavy ions of various elements have been implanted into amorphous silicon, germanium and aluminum layers at energies of 1–60 keV. High resolution ion backscattering has been used to determine range parameters and nuclear stopping powers.     

Peripheral collisions of relativistic heavy ions

The physics of peripheral collisions with relativistic heavy ions (PCRHI) is reviewed. One- and two-photon processes are discussed.     

Fragmentation of highly excited heavy ions

The observed universal momentum distribution of the fragments of a heavy ion resulting from high energy impact with a target is explained on the basis of a simple statistical model.