Stability of negative ions near the surface of a solid

Stationary states of molecular negative ions (anions) near the surface of a solid are investigated. The lone electron is assumed to interact with a diatomic molecule and the surface of the solid. The energies of electron levels are determined by solving the 2D Schrödinger equation. It is shown that its stable solutions exist at distances from the surface greater than some critical distance, otherwise the electron is detached from the anion. In the case of attraction between the electron and the solid, the interaction potential between the anion and the solid appears to have the Lennard-Jones form and the ion is separated from the surface by some equilibrium distance.     

Ion beam induced luminescence studies of LiAlO2 using negative ions

Lithium aluminate (LiAlO₂) is the candidate material for solid tritium breeder applied in the developing fusion reactors. The research of its defect behavior under ion irradiation was proceeded in the negative ions induced luminescence setup of the GIC4117 Tandem accelerator in Beijing Normal University. The ion beam induced luminescence (IBIL) measurement was performed by 20 keV H⁻ ions at room temperature. The luminescence spectra showed seven emission bands: the 4.55 eV may due to a self-trapped exciton (STE), the 4.06 eV and the 1.72 eV may due to impurity or intrinsic defect, the 3.54 eV due to F center, the 3.20 eV due to F⁺ center, the 2.93 eV due to F₂ center, the 2.30 eV due to F-center aggregates (F_n center), respectively. The intensity evolutions of each band with fluence were presented and the corresponding mechanisms were discussed.     

On beam intensity upgrade in the commercial cyclotrons of negative hydrogen ions

Compact isochronous cyclotrons to accelerate negative hydrogen ions of up to 30 MeV are widely used for production of medical isotopes and other applications. The physical and technical parameters of different accelerators are analyzed and compared. Measures to improve performance and to increase beam intensity are discussed. The text was submitted by the authors in English.     

Exact solution of the problem of quasineutral expansion into vacuum of a localized collisionless plasma with cold ions

An analytical solution of the Vlasov equation for the electrons and the hydrodynamic equations for the ions in a self-consistent electric field is constructed in the quasineutral approximation. This solution is valid for a finite electron-to-ion mass ratio. It permits describing the expansion into vacuum of a collisionless plasma with cold ions and arbitrary initial electron velocity distribution, forming a plasmoid that is bounded and, in the general case, spherically asymmetric in space. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 8, 543–547 (25 April 1998)     

Formation of negative ions in a nonideal gas

We consider a new mechanism of formation of a negative molecular ion: the decay of a localized state of an electron (a fluctuon) in a nonideal gas of polar molecules. The probability of forming a negative ion is calculated both in the quasi-classical approximation and from the solution of the nonstationary Schrödinger equation. The results from these two methods are compared.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, 83–89, November, 1987.     

Whistlers and negative ions

Using an appropriate model of the ionosphere, we find the travel time for proton whistlers to go from their source to an observer at a satellite. The results differ from earlier ones. The physical parameters obtained through whistler observations agree with these results. Damping and attenuation of whistlers are related to the ionospheric parameters.     

Kelvin-Helmholtz instability in a plasma with negative ions

A dispersion relation for low-frequency electrostatic modes in a plasma with negative ions is derived for the case in which a velocity shear Kelvin-Helmholtz instability exists in the positive ion flow along the magnetic field. It is found that the negative ions have, generally, a destabilizing effect, as seen previously for ion-acoustic and electrostatic ion-cyclotron waves. The influence of the negative-ion-to-positive-ion mass mass ratio on the stability is also examined     

Solitons in a relativistic plasma with negative ions

The interaction of the nonlinearity and the dispersiveness causing the solitary waves is studied in a relativistic plasma with negative ions through the derivation of a nonlinear partial-differential equation known as the Korteweg-de Vries equation. The negative ions play a salient part in the existence and behavior of the solitons and could be of interest in laboratory plasmas. First, the observations are made in a nonisothermal plasma, and later the reduction to the nonisothermality of the plasma shows entirely different characteristics as compared to the solitons in the isothermal plasmas. Comparison with the various solitons is emphasized     

负离子的故事

负离子广泛存在于气体、液体和固体中,参与很多重要的物理化学过程。负离子的额外电子和中性芯之间的结合很弱,这使得负离子具有显著不同于中性原子和正离子的独特性质,如负离子通常没有激发态。文章首先回顾元素周期表中各原子的电子亲和势、负离子的能级结构,以及相应的测量方法,之后详细介绍最近在过渡族元素负离子方面的研究进展,然后讨论负离子的激光冷却和偶极束缚态,最后总结和展望气相负离子相关研究。     

Photodetachment of positronium negative ions

Photodetachment of the positronium negative ion, a bound state of one positron and two electrons, has been observed. Development of a method to produce the ions efficiently using a Na coated tungsten surface has enabled the first observation of the photodetachment. The obtained lower limit of the photodetachment cross section for the wavelength of 1064 nm is consistent with the theoretical calculations reported so far. The experimental field developed in the present work gives new opportunities to explore the quantum mechanical three-body problem and to develop energy-tunable positronium beams.     

Forming a beam of ions extracted from glow-discharge plasma

In plasma-emitting structures based on glow-discharge, the potential difference between the ion-emitting plasma and the screening electrode of an ion-optic system depends on particular features of the electrode system of glow discharge and can vary in a range 0–1 kV. Results are presented of an experimental study and computer simulation of the formation of ion beams with ion energy 0–1 keV and current density 1–10 mA/cm² in ion sources based on such structures.     

Experiments on positronium negative ions

This paper is a review of new developments in the experimental field of the efficient emission of the positronium negative ion, a bound state of one positron and two electrons, from alkali-metal coated surfaces. Following the prediction of its existence by Wheeler in 1946, this ion has been one of the most attractive subjects for theorists to investigate in the field of positron physics, resulting in a large number of studies. Though the first observation of the ions, formed using a carbon thin film, was made in 1981 by Mills, there have been few experimental works since, limited by the low-production efficiency achievable for nearly 30 years. In 2008, a dramatic effect on the ion emission from tungsten surfaces was discovered upon coating it with Cs. This has opened the door to a new era of experimental investigations of this ion. This paper reports the investigations performed so far. Advances discussed include efficient formation of the ion, its photodetachment and the production of an energy-tunable positronium beam based on the technique of the photodetachment.     

Photodetachment measurements of alkali negative ions

Cross sections of alkali negative ions from 0.45 eV up to about 2.5 eV photon energy were measured. Electron affinities of the corresponding atoms are derived from the low energy onsets: EA(Li)=0.611 eV, EA(Na)=0.539 eV, EA(K)=0.497 eV, EA(Rb)=0.490 eV and EA(Cs)=0.470 eV with an estimated uncertainty of ±0.020 eV.     

The radiation of atomic negative ions

A survey is made of the experimental research program at the Fermi National Accelerator Laboratory covering the approved experimental proposals. These experiments are divided into physics topics and a comparison is made of the kinematic ranges of the measurements and the techniques used.     

Two-electron photodetachment of negative ions in a strong laser field

We study the photodetachment of H-, F-, and Br- in a short laser pulse of 800 nm wavelength and 6 x 10(14) W/cm2 peak intensity. Photoelectron spectra, recorded with the use of an imaging technique, reveal a substantial contribution from the sequential process of double detachment of halogen negative ions. The saturation effect is shown to play a crucial role in this process. The role of the alignment of atoms produced by photodetachment is discussed.     

Fusion of electron beam accelerated ions

The enhancement of neutron output when a pulsed electron beam is injected into a plasma is interpreted in terms of acceleration of a small fraction (δn/n) ≈ 10^-7 of plasma ions to MeV energies.     

High-resolution spectroscopy on a fast beam of metastable xenon ions

For the case of xenon we show that metastable ions are very suitable for optical experiments on fast ion beams (FIB experiments). It is possible to study the hyperfine structure of spectral lines in absorption from a mass separated ion beam which is exposed to a monomode laser beam. The absorption is detected by observing the fluorescence radiation. As expected, the width of the absorption signals is strongly reduced if laser- and ion-beam are parallel to each other.     

Neutralization of negative hydrogen ions in collisions with multicharged fast ions

We study the neutralization of negative hydrogen ions in collisions with multicharged fast ions (including relativistic ions) by using an approach that allows a simple expression for the neutralization cross section to be derived over a range of collision parameters where the standard Born approximation breaks down. Zh. éksp. Teor. Fiz. 115, 1549–1560 (May 1999)     

Binding-energy calculations for negative Alkaline-earth ions

The electron binding energy in negative ions of the alkaline-earth atoms Ca and Ra is calculated on the basis of the polarization potential formalism and the zeroth-approximation model relativistic perturbation theory. The results refine the published data for the sought negative ions. Odessa Hydrometeorological Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 63–67, October, 1998.     

Observation of Peregrine solitons in a multicomponent plasma with negative ions

The experimental observation of Peregrine solitons in a multicomponent plasma with the critical concentration of negative ions is reported. A slowly amplitude modulated perturbation undergoes self-modulation and gives rise to a high amplitude localized pulse. The measured amplitude of the Peregrine soliton is 3 times the nearby carrier wave amplitude, which agrees with the theory. The numerical solution of the nonlinear Schr?dinger equation is compared with the experimental results.