Auger transitions in Li-like and Be-like ions

Measurements of the Auger decay of beam-foil excited Be II and Be I levels are reported along with a proposed assignment of the experimental spectra. The Li I, Be II and Be III (1s2s²)²S → (1s²2s)²S Auger transitions as presented in this letter represents the first observation of such states in positive ions with Z?5.     

Two-electron transitions in collisions of fast multiply-charged ions with helium-like atoms

Single and double excitation and ionization of a helium-like atom are considered based on the eikonal approximation. Simple analytical formulas are derived for the cross sections of inelastic collision. A comparison with the experiment is conducted. Scientific Research Institute of Applied Physics at Tashkent State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 44–48, February, 2000.     

Lineshapes of Cd Auger MNV transitions in the metal and in CdO

The MNV Auger lineshapes are presented for Cd and for CdO and are discussed in terms of the band-like vs atomic-like picture: the Auger line-shape for CdO is compared with photoemission results. It is shown that the Auger MNV transitions are band-like in the metal, while the hole—hole interaction in the final state has a considerable importance in the oxide.     

EPR investigations of mesoporous silica doped with metal transitions ions

Electron paramagnetic resonance (EPR) experiments were performed on mesoporous silica powders in which (1,4,8,11-tetraazacyclotetradecane) cyclam groups were incorporated. These functionalised groups allow an easy binding with copper and nickel ions. Comparative studies are carried out on samples functionalised by cyclam groups located either inside the pores or in the walls of the mesoporous structures. Copper and nickel EPR parameters, including g-tensors and hyperfine components are determined and relevant electronic, magnetic and structural information are obtained. The EPR spectra intensities and line-widths are investigated on the temperature range [4 K,300 K] to clarify the relative dispersion or agglomeration of the doping ions in the matrices as well as their possible thermally activated mobility and ions pairing. As a support of the experimental EPR investigations, numerical simulations of the geometry of metallic ion environments and their electronic properties are carried out and discussed. The possibility of dynamic Jahn Teller (JT) effect in the temperature range [200, 60 K] is discussed for the nickel doped matrices where the low temperature quenched JT configuration is thought to favour the formation of Ni³⁺ pairs.     

Surface miller index dependence of Auger neutralization of ions on surfaces

Neutralization of He+ ions in grazing incidence scattering on Ag(111) and Ag(110) surfaces is studied. These measurements reveal the existence of an order of magnitude difference in the probability of ion survival on Ag(110) and Ag(111). The experimental results are discussed in terms of survival from Auger neutralization, whose rates are derived theoretically. Molecular dynamics simulation of scattered ion trajectories is performed and the surviving ion fractions are then calculated using the theoretical Auger neutralization rates, without adjustable parameters. The calculations agree quite well with the experimental data and show that the observed differences in the neutralization probabilities on these surfaces are related to different extensions of the electron density beyond the surface, resulting from different atomic packing.     

Auger transitions initiated from singly and doubly ionized states in Li metal

Major events in Auger spectra from Li surfaces containing both Na and K have been identified. Li Auger transitions initiated from both singly and doubly ionized K shells of Li have been observed. However, no higher energy satellite corresponding to the coupling of the energy of a plasmon decay with that of the Li K VV Auger electrons was detected.     

Beam-foil-excited Auger transitions in neon

Energy spectra of electrons ejected from collisions between a carbon foil and Ne projectiles with energies between 1.4 and 20 MeV have been measured. Continuous and discrete electron energy distributions are observed. Auger transitions of foil-excited Ne have been studied. Using relativistic Dirac-Fock multiconfiguration calculations, most of the measured Auger transitions have been identified.     

Auger transitions in narrow-gap semiconductors with lax band structure

Auger recombination and ionisation rates are calculated in narrow-gap semiconductor with Lax band structure⁸ such as Pb_1?xSn_xTe, Pb_1?xSn_xSe, Bi_1?xSb_x. Both low-energy (T_e? ε_g) and high-energy (ε_F ? ε_g or Te ? ε) regions are taken into consideration. In the former case we have corrected the results obtained by number of authors^3,4. The latter situation may take place in pinch channel or at the high level of laser exitation. Here we have derived the results except for constant numerical coefficient. We consider the two-particle Auger-process proposed by Emtage³ as well as three-particle ones including additional collision with acoustical phonon, charged impurity or neutral defect. The dependence of Auger transition rates upon the carrier concentration is mainly of the power-type in all variants.     

Accommodation coefficients for low-energy ions on metal surfaces

The interaction of low-energy ions (E = 3 to 100 eV) with the surface of a solid cannot be treated in terms of gas dynamics. The scattering of particles at an energy of E _o > 20 eV may be explained in terms of binary collisions with the atoms of the target. The validity of the single collision model with free surface atoms for medium energies from 10 to 100 eV and even down to 1 eV was confirmed on the basis of both experimental and computational data. This paper describes experimental studies of the secondary ion emission from the (100) and (110) faces of a Mo single crystal and both experimental and theoretical studies of alkaline ion accommodation coefficient on polycrystalline Mo within the energy range E = 3 to 50 eV with a varying direction of the primary ion beam from normal to the glancing angle of incidence (ρ = 0 to 75°). On the basis of the retarding potential method using a spherical condenser whose central electrode was the target, we measured the energy distribution of secondary ions. Calculations have been performed for the energy of scattered ions and the high energy portion of accommodation coefficient on the basis of single and double binary collisions using the Born-Mayer potential and taking into consideration the influence of adsorption forces at the surface of the target.     

Nanostructures fabricated on metal surfaces assisted by laser with optical near-field effects

Nanostructures on metal film surfaces have been written directly using a pulsed ultraviolet laser. The optical near-field effects of the laser were investigated. Spherical silica particles (500–1000 nm in diameter) were placed on metal films. After laser illumination with a single laser shot, nanoholes were obtained at the original position of the particles. The mechanism for the formation of the nanostructure patterns was investigated and found to be the near-field optical resonance effect induced by the particles on the surface. The size of the nanohole was studied as a function of laser fluence and silica particle size. The experimental results show a good agreement with those of the relevant theoretical calculations of the near-field light intensity distribution. The method of particle-enhanced laser irradiation allows the study of field enhancement effects as well as its potentialapplications for nanolithography. Received: 10 December 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003 RID="*" ID="*"Corresponding author. Fax: +65-777/1349, E-mail: HUANG_Sumei@dsi.a-star.edu.sg     

Neutron transfers and collective excitations at frontal and grazing low-energy collisions of heavy ions

Semi-classical models have been used to investigate the evolution of the wave functions of external neutrons and rotation of a deformed ¹⁵⁴Sm nucleus upon collision with a spherical ¹⁶O nucleus with energies near the Coulomb barrier. The probabilities of neutron transfers in the ⁴⁰Ca + ⁹⁶Zr reaction are determined.     

Cross sections and rate coefficients of transitions in He and He-like ions induced by collisions with heavy particles

An approach to calculating the exitation cross sections and rate coefficients for a wide class of transitions in atoms and ions induced by collisions with heavy charged particles in considered. Calculations were carried out in terms of the Born approximation in the impact parameter representation with the normalization and Coulomb repulsion (in the case of an ionic target). Transitions between levels in He and He-like ions without changes of the principal quantum number are considered for n=2–4. Fitting formulas are suggested for transition rate coefficients. Tables of cross sections and parameters of fitting formulas are given for He and C⁴⁺.