Tang Jiayong

Cross sections for 170° backscattering of 4He from oxygen in the energy range of 2.0–9.0 MeV

Abstract We report the 170° backscattering cross sections of 4He from O in the energy range of 2.0–9.0 MeV. Our measurements show that the alpha-oxygen scattering remains Rutherfordlike up to Eα = 2.35 MeV, and there exist two energy regions, 5.55–5.85 MeV and 8.50–8.80 MeV, where the cross sections present an enhanced and smooth variation. The measured cross sections in these two regions exhibit enhancement factors of 9.7 and 34, respectively, compared to the Rutherford values. In the 8.50–8.80 MeV region, the cross sections at scattering angles of 160°, 165°, 170° and 175° were measured and found to be strongly angle-dependent. The strongest resonance was seen at 7.60 MeV, where the cross section is 200 times its Rutherford value. We report the use of this resonance to measure the O areal density on a Cu surface, with a sensitivity of 1 × 1015 oxygen atoms cm 2 . We have also studied the scattering angle dependence of the threshold energy at which the cross section begins to depart from its Rutherford value. Our experimental results are not in agreement with the prediction from the analytical formula developed by Bozoian et al. [Nucl. Instr. and Meth. B 51 (1990) 311].

Radiation damage in PIXE analysis of museum paper-like objects

Abstract Paper discoloration and its tensile strength degradation caused by 2.1 MeV external proton beam bombardment under low beam current density ( 2 ) were measured as a function of the number of incident protons. The target temperature reached during bombardment was measured using an infrared thermometer. Under low beam current density, paper heating is negligible and the paper deterioration depends only on the total beam fluence. Some of the experimental results are presented and discussed for several types of paper, including one used for traditional Chinese paintings.

Comments on the classical approach to non-Rutherford cross section calculations

Abstract Non-Rutherford cross sections are needed in high energy backscattering spectroscopy. Bozoian et al. have developed a classical model and derived an analytical expression to calculate the projectile energy E nr at which the scattering cross section begins to deviate from its Rutherford value. We make comments on the model and conclude, through discussions and experiments, that (1) it is useful in estimating the energy value but gives incorrect dependences of E nr on the departure factor F and the scattering angle χ, and (2) these inadequacies originate from the classical approach, which is an over-simplified and phenomenal description of nature.

Hyperfine structure in the 576 nm line of Pr II by collinear fast-ion-beam laser spectroscopy

Atomic spectra of singly ionized praseodymium have been measured by collinear fast-ion-beam laser spectroscopy. Hyperfine structure in the 576 nm line was resolved and the magnetic dipole and electric quadruple coupling constants were determined.

Optical isotope shifts of Nd II by collinear fast-ion-beam laser spectroscopy

The optical isotope shifts in the transition - of Nd II were measured by using collinear fast-ion-beam laser spectroscopy. The changes in mean-square nuclear charge radii among five even - even neodymium isotopes were deduced from the measured optical isotope shifts: (142,144) 0.269; (144,146) 0.259; (146,148) 0.278; (148,150) 0.403. The configuration admixtures of the previously unclassified level were quantitatively analysed to be , , and with mixing probabilities of 13%, 85%, 2%, respectively.

Molecular dynamics simulation of energetic atom depositions of Au/Au(100) film

The energetic atom deposition of thin Au/Au(100) film has been studied by molecular dynamics simulation using the Au-Au interatomic interaction potential with embedded atom method. By investigating the variation of coverage curves and Bragg diffraction intensities during the film growth, the transition of Stranski-Kranstanov growth mode to Frank-van der Merwe growth mode was observed with the increase of the incident energy of deposition atoms. The role of energetic atoms in the film growth is discussed by analyzing the transport properties of deposited atoms and the evolution of incident energy and substrate temperatures.

Evaluation of non-Rutherford cross sections

Abstract The R-matrix theory is used to analyze the elastic scattering cross sections of 4 He from 16 O in the energy range 2.0–9.0 MeV. Level parameters of the compound nucleus 20 Ne, i.e., the spins, parities, resonant energies, and widths of the excited levels for alpha energies from 2.5 to 9.7 MeV, were identified. These level parameters can then be used, for application purposes, to check either the measured values of resonant cross sections or the cross sections at certain particular angles according to the experimental conditions.

ELECTRON IMPACT IONIZATION CROSS SECTION OF AR+, KR+, IN+ AND GE+

Abstract The single electron impact ionization cross sections of Ar+, Kr+, In+ and Ge+ were measured on the improved electron-ion impact apparatus at Fudan University. The Ar+, Kr+ and In+ experimental results are in good agreement with data from other laboratories. The cross section of Ge+ was measured for the first time. The experimental results indicate that the indirect ionization process gives a larger contribution to the total ionization cross section of In+, as compared to the other three targets. The experimental data were compared with our Distorted-Wave-Born-Exchange-Approximation (DWBEA) calculation, the Lotz formula, and Configuration-Averaged-Distorted-Wave (CADW) calculations.

Lifetime measurement for the (23537)°9/2 level of NdII using the collinear ion beam-laser interaction

The collinear fast ion beam-laser spectroscopy has been used to measure the radiative lifetime of the (23537)°9/2 level of the rare earth ions NdII. The measurement was carried out by the interaction between the 30keV NdII ion beam and tunable collinear dye laser which resonantly excited a metastable level to the (23537)°9/2 level, and by the observation of its time-resolved decay downstream. The lifetime value obtained from a fit program was 27.6±0.9ns. The result may provide a possibility of determining the unknown configuration of the (23537)°9/2 level.

Synthesis of a Mesoporous Manganese Dioxide-Graphene Composite by a Simple Template-Free Strategy for High-Performance Supercapacitors

A manganese dioxide (MnO2)-graphene composite material with a unique structure consisting of MnO2 surrounded by graphene sheets was prepared by a simple hydrothermal and thermal decomposition method. The morphology and structure of the obtained materials were examined by scanning electron microscopy, transition electron microscopy, Raman spectroscopy, X-ray diffraction, and N2 adsorption-desorption. Electrochemical properties were evaluated by cyclic voltammetry, galvanostatic chargedischarge and electrochemical impedance spectroscopy. The specific surface area increased from 109 to 168 m2∙g-1 for the composite containing 15% (w) graphene. The specific capacitance also increased from 294 to 454 F∙g-1 at a current density of 0.2 A∙g-1 in an aqueous electrolyte supercapacitor. Moreover, after 2000 cycles of a galvanostatic charge-discharge test, the hybrid electrode still had excellent cycle stability (92% retention rate).