Number of electrons active in slow collisions of and with

Resonant excitation or resonant electron scattering is a two step process in which Auger rates are involved in both steps. First an electron is captured into a bound state and a bound electron is excited (inverse Auger effect). Then an Auger transition leads to the emission of the electron from the ion. The corresponding cross-sections are very sensitive to the Auger rates and allow a detailed study of the Breit interaction which is a current-current contribution to the static electron-electron interaction. The contribution of the Breit interaction to the cross-section of resonant excitation on hydrogen-like uranium ions is discussed and shown that it is roughly twice as large as in the case of dielectronic recombination. Received 4 August 1999 and Received in final form 29 September 1999     

Femtosecond dynamics of adsorbate charge transfer processes

Received: 21 March 1997/Accepted: 12 August 1997     

The inversion-asymmetry of particle emission source in relativistic heavy-ion collisions

The inversion-asymmetry of the particle emission source in relativistic heavy-ion collision under the Bertsch-Pratt convention is discussed and explicitly exhibited by a Monte Carlo model. The Gaussian source function popularly used in the HBT analysis of relativistic heavy-ion collisions is invalid in this case. An inversion-asymmetric source function is suggested. A method for extracting the inversion-asymmetry degree of the source together with the source size from experimental data is proposed.     

Hardnes and resistivity of amorphous carbon thin films deposited by laser ablation

Amorphous carbon thin films were deposited by laser ablation of a graphite target, using the fundamental line of a 5 ns Nd:YAG laser. Deposition was carried out as a function of the plasma parameters (mean kinetic ion energy and plasma density), determined by means of a planar probe. In the selected working regimes the optical emission from the plasma is mainly due to atomic species, namely C⁺ (426.5 nm); however, there is also emission from other atomic species and molecular carbon. The hardness and resistivity could be varied in the range between 10 and 25 GPa, and 10⁸ and 10¹¹ Ω cm, respectively. The maximum values were obtained at a 200 eV ion energy and 6×10¹³ cm⁻³ plasma density, where the maximum quantity of C–C sp³ bonds was formed, as confirmed by Raman spectroscopy.     

A new method to study the crystallization or chemical reaction kinetics using thermal analysis technique

In this work, a new method to study the transformation kinetics is introduced. With this method, the activation energy, E_c, for crystallization (phase transition or chemical reaction), the pre-exponential coefficient of effective overall reaction rate, k_o, and the reaction order, n, can be determined. No approximation has been used in this method. This method can be used for isothermal and non-isothermal study. It is deduced from Avrami's equation without any approximation. This new method has been tested to study the amorphous-crystalline transformation kinetics under isothermal and non-isothermal conditions in the context of glassy selenium. The source of error is discussed. The calculated values of E_c, under isothermal and non-isothermal conditions are 75.3±2.5 and 79.4±2.3 kJ/mol, respectively. The predominant crystallization mechanism of the amorphous phase of glassy selenium in isothermal or non-isothermal conditions is one-dimensional growth. The deduced values of k_o were found to be 19.4±0.9 and 20.8±0.7 s⁻¹ for isothermal and non-isothermal conditions, respectively. Resulting values of the parameter, n, are compared with values obtained from other known methods used to study the reaction kinetics in thermal analyses. The difference in the results obtained with this method and the results obtained with other known methods is acceptable or lie within the experimental error range.     

Effect of residual oxygen on ionization processes of Si and Si sputtered from Si(1 1 1)-7 × 7 surface

The effect of residual oxygen impurity on ionization processes of Si⁺ and Si²⁺ has been studied quantitatively. In this study, ion sputtering experiments were carried out for a Si(1 1 1)-7 × 7 surface, irradiated with 9-11 keV Ar⁰ and Kr⁰ beam. Even if the oxygen concentration is less than the detection limit of Auger electron spectrometry, SiO⁺ and SiO₂⁺ ions have been appreciably observed. Moreover, as the SiO⁺ and SiO₂⁺ yields increases, the Si⁺ yield is slightly enhanced, whereas the Si²⁺ yield is significantly reduced. From the incidence angle dependence of secondary ion yields, it is confirmed that Si⁺* (Si⁺ with a 2p hole) created in the shallow region from the surface exclusively contributes to Si²⁺ formation. By assuming that the SiO⁺ and SiO₂⁺ yields are proportional to the residual oxygen concentration, these observations are reasonably explained: The increase of Si⁺ with the increase of residual oxygen is caused by a similar effect commonly observed for oxidized surfaces. The decrease of Si²⁺ yield can be explained by the inter-atomic Auger transition between the residual oxygen impurity and Si⁺*, which efficiently interferes the Si²⁺ formation process.     

Flat Solitary Waves due to a Submerged Body Moving in a Stratified Fluid

A theoretical model for interaction of a submerged moving body with the conjugate flow in a three-layer fluid is proposed to depict the internal flat solitary wave, which is observed in experiments conducted by the present authors. A set of coupled nonlinear algebraic equations is derived for the interracial displacements. The numerical results indicate that （a） the conjugate flow due to a two-dimensional body moving at the bottom possesses an apparent behaviour with two convex interfaces, （b） the solution satisfying the existence criterion is always unique near the relatively stable state of system. Theoretical analysis is qualitatively consistent with the experimental results obtained.     

A QCD motivated model for soft interactions at high energies

In this paper we develop an approach to soft scattering processes at high energies which is based on two elements: the Good–Walker mechanism for low mass diffraction and multi-pomeron interactions for high mass diffraction. The principal idea, which allows us to specify the theory for pomeron interactions, is that the so called soft processes occur at rather short distances (r ² ∝1/〈p _t 〉² ∝ α′_ℙ≈0.01 GeV⁻²), where perturbative QCD is valid. The value of the pomeron slope α′_ℙ is obtained from a fit to the experimental data. Using this theoretical approach, we suggest a model that fits all soft data in the ISR-Tevatron energy range: total, elastic, single and double diffractive cross sections, as well as the t dependence of the differential elastic cross section, and the mass dependence of single diffraction. In this model we calculate the survival probability of diffractive Higgs production, and we obtain a value for this observable that is smaller than 1% at the LHC energy range.     

Charged-particle multiplicity distributions in different rapidity windows in 800 GeV proton-nucleus interactions

Multiplicity distributions of charged particles produced in interactions of 800 GeV protons with emulsion nuclei in various rapidity windows are presented. The data is also analyzed separately for the forward and the backward hemispheres, for rapidity windows of different widths. It is found that the Negative Binomial Distribution (NBD) describes well the multiplicity distribution of secondary particles in various rapidity windows and also in both the hemispheres. We have compared the NBD parameters, in both the hemispheres, at 200 GeV and 360 GeV, with those at 800 GeV. The behaviour of NBD parameters in rapidity windows of different widths and for different targets has also been studied. Received: 30 August 2001 / Accepted: 28 January 2002     

Measurement of angular dependence from L3-subshell to M-shell vacancy transfer probabilities for the elements in the atomic region 71?Z?78

The angular dependence of L₃-subshell to M-shell vacancy transfer probabilities for the elements Lu, Hf, Ta, W, Os and Pt have been measured at the excitation energies of and K X-rays of Zn, Ga, Ge, and As, respectively, at seven angles varying from 120° to 150°. Energies of K X-rays are above the L₃ edge but below L₂ edge energies of the respective target elements under reference; therefore, the M X-rays are produced not only due to direct interaction of incident photons with M-shell electron but also due to the decay of L₃-subshell vacancies to M-shell. Because the angular dependence from L₃-subshell to M-shell vacancy transfer probabilities is not found in the literature, to the best of our knowledge there are no experimental values for worked elements. Therefore, the results for the elements obtained in the present study constitute the first experimental measurements and no comparison was made with other experimental and theoretical results. It has been observed that angular dependence from L₃-subshell to M-shell vacancy transfer probabilities increases with increasing .