Energies of Cu1+ ions sputtered from Cu by very low energy (50 eV < E < 1 keV) Inert gas ions

He⁺, Ne⁺ and Ar⁺ ions with energies E₁ between 50 and 1000 eV were used to bombard a polycrystalline Cu target at an angle of 45°. The energies, E₂, of the Cu₁⁺ ions sputtered at 90° to the primary beam were investigated using a UHV magnetic sector mass spectrometer. The maxima of the energy distributions as measured by the instrument, were at values of E₂ of about 4 eV (±1 eV), nearly independent of e₁ and primary ion mass. Plots of log N(E₂) versus log E₂ displayed limited linear portions over which the functional dependence of N(E₂) is proportional to E₂^?0.5. Plots of the average secondary ion energy, ē₂, versus the energy transferred by the primary ion to a Cu atom in a direct collision $\text{([}\text{4m}{}_1\text{m}{}_2\text{(m}{}_1\text{+ m}{}_2\text{)}{}^2\text{]E}{}_1\text{)}$, indicate that ē₂ increases linearly with transfer energy up to a transferred energy of about 200 eV, independent of primary ion mass. Above about 200 eV transferred energy, ē₂ asymptotically approaches values which depend upon primary ion mass. At transferred energies below about 200 eV, the collision kinematics in the fust few collisions appears to dominate the emission process.     

Transmission of low-energy (< 10 eV) O ions through Au films on TiO2(110)

In an attempt to identify the fundamental processes that influence ion transport through metallic surface layers, we have studied the transmission of O⁺ ions through discontinuous Au films adsorbed on TiO₂(110). A low energy (< 10 eV) O⁺ ion beam is generated via electron stimulated desorption when an Au-dosed TiO₂(110) substrate is bombarded with a focused 250 eV electron beam. Low energy ion scattering data indicate that Au evaporated under ultrahigh vacuum conditions at 300 K forms three-dimensional clusters on TiO₂(110). As the Au coverage increases, the formation of Au clusters on TiO₂(110) blocks a fraction of the TiO₂ surface and the O⁺ yield is attenuated. However, for high coverages (≥30% Au covered substrate) the O⁺ signal decreases at a faster rate than the TiO₂ open area fraction. We attribute the attenuation of the O⁺ yield for high Au coverages mainly to blocking of O⁺ by Au clusters, to deflection of trajectories by the image force between ions and Au clusters, and to charge transfer between desorbing O⁺ and neighboring Au clusters.     

Study of the sputtering of adsorbates by low energy ions (O on Ni)

Sputtering or ion impact desorption of adsorbed layers has been studied by low energy ion scattering and model calculations. For adsorption of a monolayer or less (e.g. oxygen on nickel) the desorption by ions can be readily observed by He⁺ ion scattering from the development of the adsorbate and substrate signal as a function of time. Desorption cross sections for Ne⁺ and He⁺ ions in the energy range from 500 eV to 1600 eV are given. These results are compared with the model calculations and the influence of various parameters can be studied by this comparison. The contribution of different processes to the sputtering mechanism is discussed.     

Method for measuring the PCR proton spectrum in the energy range of > 10<Superscript>16</Superscript> eV

Criteria for selecting proton events among the total sequence of events from primary nuclei of cosmic rays with zenith angles θ < 20° are analyzed in the energy region of E ₀ ≈ 10¹⁶ eV. These criteria are concretized for the case of the SPHERE-2 experiment geometry. The QGSJET-I and QGSJET-II model calculations show that the criteria based on the shape of the transverse distribution of Cherenkov light allow detection of more than 10% of proton events and rejection of 99% nuclear events.     

Passage of electrons through thick layers of material (energy distribution)

A magnetic -spectrometer has been used for a thorough study of the energy distribution of electrons having an initial energy of 6.74 MeV after passage through C, Al, Cu, Sn, and Pb samples up to 0.5 R in thickness.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 12, No. 6, pp. 12–15, June, 1969.     

Particles of primary cosmic radiation generating extensive air showers of energy above 10<Superscript>20</Superscript> eV in the atmosphere

In order to construct the energy spectrum on the basis of data from the Yakutsk array, a method similar to that employed at the AGASA array is applied in addition to the standard approach based on experimental procedures. Moreover, a new, original, method underlying the calculation of the spectrum in the region of energies above 10²⁰ eV is used to estimate energies. In order to compare data obtained at different arrays, it is proposed to harness the universal spectrum based on HiRes data. Within the QGSJET2 model, it is shown that a shower of energy 2 × 10²⁰ eV was observed at the Yakutsk array. In the same energy region (above 2 × 10²⁰ eV), the AGASA array recorded four showers, while the Fly’s Eye array and Pierre Auger Observatory (PAO) recorded one shower each. These data do not confirm the conclusion that the flux of primary-cosmic-ray particles decreases because of the Greisen-Zatsepin-Kuzmin effect.     

Direct stratospheric measurements of charges and energies of Primary Cosmic Rays in the range of 10<Superscript>13</Superscript> − 10<Superscript>15</Superscript> eV (CROSS Project)

The CROSS (Cosmic Rays Over Spectrum Steepening) experiment is aimed at direct measurements of masses and energies of primary cosmic ray (PCR) nuclei in the range of 10¹³ ? 10¹⁵ eV near the break in the PCR energy spectrum. The experimental equipment includes a balloon ionization spectrometer consisting of X-ray transition radiation generators interlaid with thin-wall proportional chambers.     

Study of the angular and energy distributions of Na+ and K+ ions which have passed through thin copper films

The angular and energy distributions of alkaline Na⁺ and K⁺ ions which have passed through thin Cu films in different crystal states are studied. The ion energy E₀ is varied from 10 to 40 keV, and the incidence angle. ranges from 0° to 60°. The angular aperture of the detector is ～0.5°, which allows the form of the angular distribution of ions which have passed through the solid thin films as a function of the energy, the angle of primary-ion beam incidence, and the layer thickness to be studied in detail. It is shown that, in the range E₀ = 10.40 keV, the energy loss ΔE of those ions that have passed increases linearly as the energy of incident ions increases. The energy loss increases with increasing ion mass in the case of singly charged ions. The surface amorphization of single- and polycrystalline films leads to an increase (by 150–200 eV) in the energy loss caused by the diffuse propagation of ions and to loss-peak broadening. It is probable that surface amorphization is accompanied by an increase in the number of atoms experiencing multiple collisions with atoms of the film, which leads to an increase in the average energy loss by ions that have passed through films.     

Neutrinos of energy approximately 10(16) eV from gamma-ray bursts in pulsar wind bubbles

The supranova model for gamma-ray bursts (GRBs) is becoming increasingly more popular. In this scenario the GRB occurs weeks to years after a supernova explosion, and is located inside a pulsar wind bubble (PWB). Protons accelerated in the internal shocks that emit the GRB may interact with the external PWB photons producing pions which decay into approximately 10(16) eV neutrinos. A km(2) neutrino detector would observe several events per year correlated with the GRBs.     

Multiple scattering and neutralization aspects of low energy noble gas ions incident on a Cu (110) crystal

Experiments have been done with 1 keV Ne⁺ ions bombarding a Cu (110) single crystal in a (111) plane. From the measured energy spectra of the scattered ions the minimum and maximum scattering angles for multiple scattering on the surface are determined. These minimum and maximum scattering angles were also calculated using a computer model. The parameters for an interatomic potential function between ion and metal atom are determined by comparison of the experimental and calculated scattering angles. A neutralization model for an energetic ion at an atomic surface is given. The reliability of this model is tested by comparison of the results of computer calculations and the measured peak intensity distributions as a function of the scattering angle.     

N2O+离子A2∑+电子态的光解动力学研究

用一束波长为360.55nm的激光,通过N2O分子的(3+1)共振多光子电离(REMPI)过程制备纯净且布居完全处于X2Ⅱ(000)态的母体离子N2O+,然后用另一束波长在275-328nm范围内的可调谐激光将制备的N2O+离子激发至预解离电子态A2∑+.实验发现,由于解离碎片NO+所具有的一定的反冲速度,其TOF质谱峰明显比N2O+母体宽.通过分析NO+碎片TOF质谱峰形状,得到了解离产物的总平均平动能;通过考察随光解能量的变化,发现光解能量在32000cm-1附近约250cm-1的变化范围内,值由约8000cm-1突然减小至约1600cm-1.通过分析,在光解能量小于32000cm-1的区域,解离通道为NO+(X1∑+)+N(4S);而在光解能量大于32000cm-1的区域,另一个具有较高解离限的解离通道,NO+(X1∑+)+N(2D),开启并完全取代N(4S)通道成为解离的惟一通道.根据实验结果,对在所研究的光解能量范围内的N2O+离子A2∑+电子态预解离机理进行了探讨.     

Microstructural and magnetic properties of thick (≥10 μm) magnetron sputtered barium ferrite films

This work focuses on the properties of 10-15 μm thick barium M-type hexaferrite (BaFe₁₂O₁₉ or BaM) films deposited by non-reactive RF magnetron sputtering on alumina substrates. High deposition rates were achieved through deposition at room temperature and operation at an RF power of 100 W. By varying sputtering gas pressure, the dc magnetic properties were correlated with structural, morphological and compositional properties obtained by X-ray diffraction (XRD), atomic force microscopy (AFM) and Rutherford backscattering spectrometry (RBS), respectively. A deposition pressure of P=3 Pa enables one to reach the best compromise between high deposition rate (0.75 μm/h) and adequate crystallographic, stoichiometric and magnetostatic properties. Finally the gyromagnetic properties at high frequency were assessed through the characterization of coplanar isolator up to 60 GHz. As such, hexaferrite films prepared using this technique may offer opportunities for the next generation of self-biased planar microwave devices.     

Efficiency of the production of γ families with halos and the fraction of protons at an energy of 10<Superscript>16</Superscript> eV

γ Families with halos detected in the “Pamir” experiment have been analyzed. Comparison of the experimental data with the results of calculation within the quark-gluon string model (MC0 code) made it possible to determine the efficiency of halo formation by protons, α particles, and heavy nuclei, as well as the fraction of protons in the mass composition of primary cosmic rays at an energy of 10¹⁶ eV. It is shown that halos are formed predominantly by protons. The fraction of protons in the mass composition of primary cosmic rays at an energy of 10¹⁶ eV is 20%.     

Interaction of low energy (5–10 keV) argon atoms and ions with a Cu(100) surface; Ion fraction,ionization and neutralization

The ion fractions η⁺ of low energy (5–10 keV) argon particles scattered from a Cu(100) surface, are measured with a time of flight spectrometer. Neutral as well as charged projectiles are used. The scattering angle θ is 30°. The results for different angles of incidence ψ and crystal directions are reported. For scattering in the 〈100〉 direction, with a ψ-value of 15° and a primary energy E₀ of 5 and 10 keV, the ion fractions for the quasi single scattering peak, η⁺_QS, are 1.5 and 6.1% respectively. When E₀ is between 5 and 10 keV a reionization process with a constant reionization probability occurs during the violent interaction. This process, but also neutralization along the outgoing trajectory, determines η⁺_QS. With ions as projectiles, an energy difference of about 16 eV is observed between the quasi single scattering peaks in the spectra of all scattered particles and of ions only. The ion fraction for the quasi double scattering peak, η⁺_QD. depends largely upon E₀, indicating that the efficiency of the reionization process increases with E₀. A qualitative discussion of the data is given, using the reionization process and the interatomic neutralization processes along the trajectory of the scattered particles.     

A molecular dynamics simulation of ultrathin oxide films onsilicon: Growth by thermal O atoms and sputtering by 100 eV Ar+ ions

Molecular dynamics was applied to study the growth and sputtering of ultrathin oxide films on (100) Si surfaces. A multibody potential which stabilized the Si/SiO₂ interface was used for this purpose. Oxide growth by exposure to O atoms was found to follow Langmuir-type kinetics with unity initial sticking coefficient of O and saturation coverage of around four monolayers, in agreement with experimental data. Sputtering of an ultrathin oxide film on silicon by 100 eV Ar⁺ ions was simulated to study ion-assisted surface cleaning. Ion irradiation was found to promote restructuring of the surface into oxide islands, as observed experimentally. Island formation was accompanied with an increase in surface roughness. The evolution of the surface state with ion dose was predicted quantitatively     

Elastic and inelastic processes in the interaction of 1–10 eV ions with solids: ion transport through surface layers

We review the escape depth of secondary ions (or neutrals) desorbing from solid surfaces under the impact of electrons, photons or ions. We survey ion (or neutral) transport through many materials, but most are wide band gap insulators such as rare-gas solids and molecular solids. We address the issue of low-energy (<10 eV) ion—solid interactions, and review experimental and theoretical studies that provide insight into the physical mechanisms of these interactions, such as elastic scattering, charge transfer and ion—molecule reactions. Although it is usually assumed that most of the secondary ions stem from the top surface layer, we show that this is not necessarily the case: In certain instances, 1–10 eV ions are able to transmit solid films which are several monolayers thick. The transport of low-energy ions through materials has very broad implications. We point out the importance of these results for electron or photon stimulated desorption (ESD/PSD), secondary ion mass spectrometry (SIMS), and ion-sputtering of surfaces, and discuss their relevance to other fields, such as ion beam deposition (IBD), low-energy ion implantation, and electrochemistry.     

Cosmic ray energy spectrum (>1017 eV) of the Yakutsk EAS array

The energy spectrum obtained on the Yakutsk array for the parameter S ₆₀₀ is compared with the results obtained on the AGASA and HiRes arrays and the latest Pierre Auger Observatory data. The discrepancy in the intensity of the energy spectra obtained in different experiments can be explained by the presence of systematic errors in shower energy estimations.