Progres in ion beam analysis at Fudan University in the recent years is briefly reviewed. Presented as examples of the research activities performed in this field are the following projects: (1) Nuclear potential resonance scattering of 6.25 MeV and 4.25 MeV helium ions for simultaneous compositional analysis of carbon and oxygen in a Mylar, a SnInO, and some other film samples: (2) Determination of stoichiometry of a high-temperature superconducting Y-Ba-Cu-O sample by backscattering of 8.8 MeV helium ions; (3) Backscattering and channeling analysis of multilayered structures periodically consisting of layers of pure Si and alternate layers of Ge and Si, grown on (100) Si substrates by molecular beam epitaxy: (4) Studies of surface structure of Al(100) by the use of MeV ions backscattering and channeling surface peak: and (5) MeV ion microbeam analysis and the use of PIXE method in DNA study. etc.

Beginning from the proposition that availability of reliable data is necessary to the application of nuclear techniques, we explore the questions of how such data are obtained and how the extent of their reliability is ascertained. These questions are considered first in general terms in relation to data types and organizational frameworks, then with particular reference to the journal Atomic Data and Nuclear Data Tables. The reliability issue is further discussed in terms of this journal's policies and unique presentation style.

On the basis of general description of AMS, the advantage and development of tandem accelerator based AMS are discussed. The AMS facility at Peking University and its preliminary applications are described.

The structure consideration of a minicyclotron as super- sensitivity mass spectrometer for carbon-14 dating being constructed at this Institute is described. Some new design ideas and techniques are presented.

Mössbauer effect, a nuclear analogue of resonance fluorescence, has proven to be one of the most effective experimental methods for the scientific investigation in a large variety of problems from nuclear physics to medicine. The popularity of the method is due to the fact that it allows one to carry out experiments with the highest energy resolution. Approximately 1000 articles have been published during each of the last 10 years. In this review, we will discuss some of recent developments in this field, the applications in natural science, and some industrial applications. Finally, the general conditions of Mössbauer spectroscopy will be discussed and the present situation of this field in China will be involved.

Research on accelerator-based atomic physics at the Lawrence Berkeley Laboratory super - HILAC and Bevalac accelerators is described. This research covers several important topics in collisions of fast, highly charged ions with atoms: charge transfer, ionization, and excitation. Multiple-electron processes are emphasized. Electron correlation is important in some of these processes, e.g., resonance transfer and excitation (RTE) multiple-electron capture in close collisions. A variety of experiments and results for energies from 1 to 420 MeV/u are presented.

The electonic transition rates in low - energy ion-surface interaction were studied by emplaying tilted-foil and grazing incidence geometries, and the linear and circular polarizations of light emitted were observed, respectively. The theoretical understanding of the dynamics is still expected.

Microclusters from different structures of silicon and carbon are studied by SIMS under UHV conditions in the mass range below M = 200. The sputtered mass spectra of ions Sin+, Cn+ and C_n were obtained from the 10 keV O2+ primary beam bombardment. Comparisons of each spectrum in each group have shown the strong structure effects on the cluster patterns. A brief discussion on the results has been given.

The principles of positron annihilation and four positron experimental techniques are described. The application of positron annihilation technique in material science, atomic physics and other related fields are discussed.

Resonances in the reaction ¹⁹F (α, p) ²²Ne have been used to detect and depth profile ¹⁹F in solid targets. Incident alpha particles in the range 2100-2500 keV were used and protons were detected at θ = 135° with a large solid angle surface barrier detector covered to stop elastically scattered alpha particles. This technique is a simple, nuclide specific probe and is particularly useful in detecting ¹⁹F in the presence of heavy elements such as GaAs where conventional Rutherford backscattering is ineffective. Examples using this technique on epitaxially grown thin films containing LaF₃ layers will be presented.

The reaction ¹¹B(p, α) ⁸Be was used to profile boron concentration in silicide. The energy of incident proton of 2.4 MeV was selected. The samples were Ti silicide implanted with 80 keV and 230 keV BF₂. The experimental results indicate that the behaviour of boron is different from that of fluorine during silicide formation.

¹H or ⁴He depth profiling in ¹H or ⁴He implanted silicon samples was performed by elastic recoil detection (ERD) with multicharged ¹⁹F ions at a small accelerator. Optimization of the experimental parameters such as incident ions energy and scattering geometry were calculated by computer simulation. Depth resolution of about 20-30nm at depth of 400nm for ¹H and at depth of 300nm for ⁴He can be obtained, respectively.

The State University of New York at Albany ion scanning microprobe has been used for materials characterization. Focused proton and helium ion beams have been used. Rutherford backscattering spectroscopy (RBS) and particle - induced X-ray emission (PIXE) analysis have been performed on microelectronic circuits with a spatial resolution of approximately 2 µ m. Studies on thin films of superconductors will be presented. Several examples of chemical and microstructural analysis will be given.

IXX (or PIXE - induced XRF) technique gains two main advantages over conventional PIXE method. First, it can be used to avoid or significantly reduce background and spectral interferences from major elements in the sample by proper selecting the primary target. Second, target damage is greatly reduced, so that it is more suitable for the analysis of heatsensitive and delicate specimens. A new IXX system with a very tight geometry is described. Some of its performances and preliminary applications are presented.

A computer program MACA was developed for simulating high - dose ion implantation into amorphous solids. The topology of amorphous solids was modelled by adjusting the free flight path distribution between collisions, so that the radial distribution function will characterize the short - range order and long - range disorder of amorphous targets. A simulation example is given.

A copper based binary alloy containing 16.9 at % lithium has been bombarded with deuterium ions in energy range of 400 eV to 2 keV at the incidence angles of 70° and 80° away from the surface normal. The sputtered flux was condensed on Al-strips arranged arround the target in a cylindrical cup. 1.5 MeV proton backscattering and nuclear reaction ⁷Li(p, α)⁴He were used to detect the collected atoms of Cu and Li simultaneously. The angular distribution of sputtered atoms has been shown to be different for two components and strongly anisotropic for the grazing incidence. According to direct knock-on sputtering model and the experimental results the angle for the maximum differential sputtering yield is dependent on the incidence angle α, the bombarding energy E, the energy transfer factor γ=4M₁M₂/(M₁+M₂)² and the surface binding energy U. With the assumption that the sputtered particles are diffracted by a planar barrier the surface binding energies of 2.3 eV for the Li component and 3.0 eV for the Cu component have been determined by fitting the measured angles of preferred ejection to the direct knock-on sputtering model, and the results agree well with a pair-binding model.

High energy ion backscattering can be used to enhance the sensitivity of oxygen analysis. At He⁺⁺ ion energy of 8.8 MeV, the yield due to oxygen is about 25 times larger than that predicted by Rutherford formula. The elemental stoichiometry of some bulk and thin film superconductor samples was determined. The details of the measuring method are discribed.

Elastic recoil detection (ERD) proposed for the analysis of light elements in a heavier matrix is an appropriate method for its specialities. Optimization of experimental parameters in ERD such as scattering geometry and incident beam energy is very important when using a small accelerator with energy lower than 10 MeV. In this paper a computer program ERDA1 is developed for the purpose, and is proved to be useful for practical handling of ERD experiments.

Implantations of 100 keV In ions to high dose of 6×10¹⁶In/cm² were performed into a-axis oriented crystals of Al₂O₃ held at a liquid nitrogen temperature. The implantation produced about 80nm thick amorphous surface layer. Isothermal annealing in flowing Ar gas ambient was done at the temperatures of 600, 700, 800, and 900℃. Rutherford backscattering and channeling (RBS-C), scanning electron microscope (SEM) and reflection high energy electron diffraction (RHEED) have been employed to investigate the annealing behaviors.The indium shows anomalous diffusion in amorphous layer. The migration of indium was composed of two parts: (a) some broadening of In profile corresponding to diffusion within the amorphous layer, (b) segregation of In to surface to form In₂O₃ which appears as islands on the surface. When the ambient is made oxygen free, the segregated In is lost by evaporation at the surface.

A UHV system specially designed for studying surface and interface atomic structure by MeV ion scattering and channeling is described. The vacuum in the UHV chamber is 133.332×10^-10Pa. The chamber is equipped with an ion gun used for sample cleaning, a translatable four-grid LEED-Auger system used for characterization of the crystal surface, and a three dimensional goniometer. The crystal preparation and cleaning procedure of Al(100) are presented. The surface peak intensity of Al(100)-< 100> and Al(100)- <100> has been measured by MeV ion channeling and scattering. The measured surface peak intensity was compared with that of Monte-Carlo simulation. The experimental results indicate that the thermal vibration amplitude of Al(100) surface atoms is 1.2-1.3 times that of bulk atoms. The relaxation of first layer for Al(100) is less than -0.005nm.

Rutherford backscattering spectroscopy (RBS) with channeling technique has been used to analyze the damage and its annealing of Si⁺ and P⁺ implanted InP:Fe. 150 keV Si ions and 160 keV P ions were implanted with doses ranging from 1×10¹³ to 1×10¹⁵/ cm² at room temperature, 200℃ and 77K. Thermal annealing was performed in a conventional open tube furnace under flow of pure N₂ for 15 minutes. Annealing temperature was chosen from 150℃ to 800℃. It was found that a dose of 8×10¹³/cm² Si⁺ was sufficient to produce an amorphous layer at room temperature and its epitaxial regrowth takes place at temperature below 150 ℃. The epitaxial regrowth of amorphous layer produced by 1×10¹⁴/cm² Si ions occurs from both substrate and surface while that produced by co-implantation of 1×10¹⁴/cm² Si ions with the same dose of P ions takes place from substrate only. It was also noticed that for the former sample, its amorphized layer can be nearly completely recrystallized by epitaxial growth at 650 ℃, but for the latter much residual disorder remains even after annealing at 750 ℃. As for 77K implant at dose as low as 5×10¹³/cm², Si ions begin to produce an amorphous layer that can be wholly reordered at 750℃. Samples implanted at 200℃ remain crystalline only with small fraction of disorder due to self-annealing effect during the implantation. The damage annealing in the implanted layer corresponds to the change of electrical parameters got from Hall measurements.

Hydrogen contents and its depth profiles, obtained by nuclear reaction induced by fluorine ion, have been investigated for a series of thermal annealed amorphous silicon and implanted amorphous carbon (diamond-like carbon) films. For dual layer amorphous silicon films, it is shown that hydrogen of either a-Si:H or a-SiNx:H sublayer moves obviously at different annealing conditions. For diamond-like carbon (DLC) films, measurements show that, by argon implantation, hydrogen contents decrease obviously with the increase of implanting dose. The decrease of hydrogen contents results in the decrease of diamond-like (SP³) and graphite-like (SP²) components of DLC films. But, the ratios of SP² and SP³ increased, and the resistivities decrease with the increase of implanting dose.

Structures and properties of both isolated and compacted clusters can be studied by SINS, RBS, NMR and Mössbauer effect, etc. Some important properties of these microclusters, such as magic numbers, isotopic effect, gas-like structures are discussed.