Yang Fujia

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].

PIXE-induced XRF with transmission geometry

Abstract PIXE-induced XRF, or PIXE-XRF, is an analytical method using nearly monoenergetic X-rays from the particle bombardment of a primary target to induce X-ray fluorescence. This method gains two main advantages over the conventional PIXE method. First, with the proper selection of the primary target, the spectral interferences from major elements in the sample can be eliminated. Second, sample damage is greatly reduced, so that it is more suitable for the analysis of heat-sensitive, volatile and delicate specimens. In the present paper, a transmission geometry of the primary target for PIXE-XRF is proposed. The primary X-ray yields were calculated as the functions of primary target thickness for proton and helium particles at various energies. The selection of experimental conditions, including the primary target thickness, the ion beam and its energy, is discussed. The preliminary experimental results showed that with the transmission geometry the characteristic X-ray yields of the specimen were two orders of magnitude higher than those obtained with the reflection geometry arrangement, enabling the detection limits for both the thin and the thick target to reach sub-ppm level. Some preliminary applications are presented.

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.

Archaeological applications of PIXE and IXX for paperlike objects at Fudan University

Abstract The PIXE and IXX analyses of paperlike museum objects at Fudan University are summarized. Emphasis is laid on preventing the samples from being damaged by irradiation. An on-demand beam pulsing system is useful for the PIXE analysis of delicate objects. IXX is more suitable in terms of damage compared to PIXE. Some PIXE and IXX applications of archaeological paperlike samples are given.

NON-DESTRUCTIVE ANALYSIS AND APPRAISAL OF PAPER-LIKE OBJECTS

Abstract This paper reports the experimental results of external proton beam radiation damage on paper. The damage effect was observed by the tensile strength degradation and the change of the structure measured by XRD. The limit doses of 2.5–3.5 MeV proton beam for some kinds of paper are given. This paper also reports the experimental results of the identification of some Chinese stamps of different editions. The proton induced X-ray emission (PIXE) method has also been used to identify forged notes, including false Renminbi and US Dollar found in China. The PIXE spectrum measured from the forged notes shows that the elemental composition is different from that of genuine ones. The PIXE spectra from the forged notes made by different counterfeiters are different from each other. So the PIXE method is a helpful tool to unveil the provenance of the forged notes.

Experimental Study of Single-Electron Detachment Cross Sections of Cu- in Collision with He

The single-electron detachment cross sections of Cu- in collision with He have been measured in the range of 10-30 keV by a growth rate method. The typical value of the cross section is 7.63×10-16cm2 at an energy of 20 keV. The experimental uncertainty of the results is about ±8%.

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.

Single-Electron Detachment for Transition Elements Cr−and Fe− in Collision with He

Single-electron detachment (SED) cross-sections for Cr− and Fe− in collisions with He have been obtained in the energy region of 10–30 keV for the first time. In the present energy range the magnitude of the Cr−+ He SED cross-sections is close to that of Fe−+ He, although the electron affinity of Fe− (0.16 eV) and Cr− (0.668 eV) are different. It is found that the cross-sections for Cr− and Fe− in collisions with He exhibit nearly the same dependence on anions impact velocity.

Changes of the Nuclear Charge Distribution of Nd from Optical Isotope Shifts

The isotope shifts and hyperfine structures of seven optical transitions for all seven stable isotopes of Nd II were measured by using collinear fast-ion-beam laser spectroscopy. The nuclear parameter λ was obtained from the measured optical isotope shifts for all seven stable isotopes with improved accuracy. The λ values were analysed by using the Fermi distribution for the nuclear charge density. The values of δr2, δr4 and δr6 were determined.