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... The ion energy in the experiment was near Coulomb barrier, so, X-rays from projectile-like ions are also expected. The nuclear product Cr is one of the candidates for nuclear product forms by the alpha transfer reaction [23,24]. The energy of the second peak is also matched with the K a transition from He-like Cr [20], however, the detector resolution was not good enough to resolve. ...
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The differing results of previous analyses of the binding energy for particles trapped in the wake of fast-moving ions traversing a solid are reconciled, and the values given by Day are corrected at high velocities. A form of a variational calculation of these energies which permits comparison of various dielectric functions is presented, and used to deduce a possible form for the bound-particle wave function. This wave function is used in an analysis of processes occurring as the wake emerges from the surface.
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We have investigated the electron capture into large-l Rydberg states of multiply charged ionic projectiles (e.g., the core charges Z=6, 7, and 8) escaping solid surfaces with intermediate velocities (v≈1a.u.) in the normal emergence geometry. A model of the nonresonant electron capture from the solid conduction band into the moving large angular-momentum Rydberg states of the ions is developed through a generalization of our results obtained previously for the low-l cases (l=0, 1, and 2). The model is based on the two-wave-function dynamics of the Demkov-Ostrovskii type. The electron exchange process is described by a mixed flux through a moving plane (“Firsov plane”), placed between the solid surface and the ionic projectile. Due to low eccentricities of the large-l Rydberg systems, the mixed flux must be evaluated through the whole Firsov plane. It is for this purpose that a suitable asymptotic method is developed. For intermediate ionic velocities and for all relevant values of the principal quantum number n≈Z, the population probability Pnl is obtained as a nonlinear l distribution. The theoretical predictions concerning the ions S VI, Cl VII, and Ar VIII are compared with the available results of the beam-foil experiments.
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A complete experimental study of the production and transport of long-lifetime excited states has been done for Ar18+ on solid C targets, at a velocity of 23 a.u., and for a range of thickness allowing us to vary the transport conditions from single collision to equilibrium (3.5 to 201 μg∕cm2). A systematic determination of Ar17+ Rydberg ℓ- and 2s-state populations has been performed using the x-ray spectroscopy technique. Results are compared with predictions of different transport simulations (developed on either a quantum or a classical phase space), which take into account multiple collisions and the strong polarization induced by the incoming ion (the wakefield). Using the continuum distorted-wave approximation for modeling the initial capture process, very good agreement is found between experimental Rydberg-state populations and theoretical approaches limited to the effect of multiple collisions. On the contrary, the transport of the metastable 2s state exhibits strong sensitivity to Stark mixing induced by the wakefield. The limitation of each theoretical approach is discussed with respect to the different experimental observables.
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Results of various fusion experiments with heavy ions are compared with predictions of statistical model calculations. In some reactions there is evidence for nonstatistical effects based on significant discrepancies between the calculations and the experimental results. Alternative explanations of these discrepancies are considered.[NUCLEAR REACTIONS HI (xnγ), statistical model calculations.]
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A facility for lifetime measurement of metastable states in highly charged ions using the beam-foil technique with a single-foil and a two-foil target has been developed. In the two-foil technique, one foil moves with respect to the other and the option of varying the thickness of the fixed foil online has been implemented. A holder with multiple foils is used as a fixed target, and moved along x, y, and θ, the angle of rotation with respect to beam direction along the z axis. Using this facility, the He-like 1s2p and Li-like 1s2s2p titanium lifetimes have been measured and compared with earlier values. In addition to this, the processes which occur when excited states collide with carbon foils of different thicknesses have also been investigated. Preliminary results suggest the scope of studying intrashell transitions during ion-solid collision using this setup. In this article, the setup is described in detail and representative results are briefly discussed.
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We report collision-induced intra-shell transitions for the first time. It has been observed between two close by levels 1s2s 3S1 and 1s2p3Po2 in He-like Ti ions by the beam-two-foil time-of-flight technique. The mean collision-induced transition probability between these two levels is found to be quite large (0.72 ± 0.05/collision), which is attributable to the small energy splittings (32 eV) between them.
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The wavelengths, radiative transition probabilities and autoionization rates have been calculated for the transitions 1s2l3l'-1s2 2l in a wide range of nuclear charge Z. These data were used for the calculation of relative intensity factors Qd for dielectronic satellite of highly charged He-like ions. Synthetic spectra will be built from these data for different plasma sources. A perturbation theory method is described for the calculation of atomic properties of autoionization states. Correlation, relativistic and radiative effects were taken into account. Z-dependencies of radiative transition probabilities and autoionization rates are discussed. Relative intensity factors of dielectronic satellite lines are shown as functions of Z for different types of 1s2l3l'-1s2 2l transitions.
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Using projectile-like ions instead of projectile ions in a beam–foil source, we have reconfirmed the formation of circular Rydberg states. The projectile-like 6028Ni and 6329Cu ions have been produced by a 5626Fe ion beam and 6230Zn ions by a 5828Ni ion beam, at beam energies above the Coulomb barrier, bombarding a thin carbon foil. Time-resolved x-ray transitions of these projectile-like ions attain their maximum intensities at different delays. Such delays are attributed to successive cascading through yrast transitions from the circular Rydberg levels, which find important implications in understanding the origin of radio recombination lines from interstellar space.
Article
We observed the circular Rydberg states populating H-like Fe ions during fast ion-solid collisions. Time-resolved X-ray spectra obtained with 164 MeV 5626Fe ions colliding with a carbon foil do not show any lines due to H-like Fe ions at small delay times until 600 ps. However, Lyα and Lyβ transitions appear after a while and attain maximum intensity at a delay of 920 ± 5 ps. Such a delay is attributed to successive cascading from the circular Rydberg levels, which has important implications for understanding the origin of radio recombination lines from interstellar space.
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Bulk and surface plasmon excitations in amorphous carbon (a-C) films have been characterized by core-level loss spectroscopy. Atomically smooth a-C surfaces were used in their as-grown state, after UHV annealing and after covalent immobilization of dense molecular monolayers (2–4 × 1014 cm−2), either perfluorinated or labelled with an ester functionality. X-ray photoelectron spectra reveal a sp3-rich hybridization of surface C atoms, with a σ + π plasmon loss distribution centred at 29.5 ± 1 eV, characteristic of a high electron density value. For molecular grafted surfaces, the energy distribution of plasmon losses reveals new contributions in the range 15–25 eV (clearly separated from the energy distribution of the bulk σ + π plasmon loss of a-C) with an increasing loss probability observed at grazing photoemission angles. A simple parameterization method is presented to derive bulk and surface plasmon loss distributions from angular core level loss spectroscopy (XPS) data, without a priori assumptions on the shape of the loss energy distributions.
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Delayed beam-foil X-ray spectra of highly charged ions of V, Fe and Ni show a few lines at energies higher than the H-like Lyman α-line of the respective projectile ions. These can only be attributed to heavier ions. Further the time dependence of such unexpected lines display a peculiar behavior. This work presents the experimental observations systematically.
Article
A computer program calculating charge state distributions of ions with up to 28 electrons distributed over n = 1, 2 and 3 subshells has been developed. The model is based on an independent electron model taking into account electron loss, capture and excitation from and to all the subshells. Calculated atomic cross sections are recomputed periodically to take into account their dependence with the projectile energy and its mean charge state when they vary as a function of target thickness.
Article
The decay curves for 2p-1s and 3p-1s transitions in 32-MeV H-like oxygen projectiles excited by a thin carbon foil have been measured and compared with the results of a cascade computer program which calculates the intensities of these transitions for an assumed initial distribution of excited states as a function of decay time. The measured decay curves agreed best with those predicted by the cascade program using an l-independent population probability proportional to n/sup -4/ for each state.
Article
The experimentally observed high-{ital l}-state population of ions excited in ion-solid interactions differs sharply from {ital l}-state populations produced in ion-atom collisions. We have studied the population dynamics of electronic excitation and transport within the framework of a classical transport theory for O{sup 2+} (2-MeV/u) ions traversing C foils. The resulting delayed-photon-emission intensities are found to be in very good agreement with experiment. Initial phase-space conditions have been obtained from both classical-trajectory Monte Carlo calculations and random initial distributions. We find evidence that the very-high-{ital l}-state populations produced in ion-solid collisions are the result of a diffusion to high-{ital l} states under the influence of multiple scattering in the bulk of the solid.
Article
Projectile-centered Rydberg states of highly charged fast ions traversing thin solid targets show an unexpected abundance of high-l states. We present a theory for the production of high-l states based on classical stochastic dynamics. Diffusion into high-l states is shown to be universal for single-particle orbits in three dimensions under the influence of a stochastic perturbation, i.e., largely independent of the details of the interaction potentials. Monte Carlo simulations using a Langevin equation for stochastically perturbed electrons in a dynamically screened Coulomb field yield quantitative agreement with experimental data.
Dielectronic satellite spectra of the ls3p-1s 2 lines for highly-charged ions with Z¼
  • Ui Safronova
  • Ms Safronova
  • R Bruch
  • La Vainshtein
Safronova UI, Safronova MS, Bruch R, Vainshtein LA. Dielectronic satellite spectra of the ls3p-1s 2 lines for highly-charged ions with Z¼ 6–54 (1s2l3l 0 À 1s 2 2l transitions). Phys Scr 1995;51:471–83.
NIST Atomic Spectra Database (ver.4.1.0), [Online]. National Institute of Standards and Technology Available from
  • Ralchenko Yu
  • Ae Kramida
  • J Reader
  • Nist
  • Team
Ralchenko Yu, Kramida AE, Reader J. NIST ASD Team, NIST Atomic Spectra Database (ver.4.1.0), [Online]. National Institute of Standards and Technology, Gaithersburg, MD; 2011. Available from: /http://physics.nist.gov/asd3S [03.09.12].