Acta Physica Sinica (Overseas Edition), 1993, Vol. 2(9): 641-647    DOI: 10.1088/1004-423X/2/9/001
 NUCLEAR PHYSICS Next

# THE STUDIES OF NON-RUTHERFORD BACKSCATTERING CROSS SECTIONS OF 4He FROM 16O

CHENG HUAN-SHENG (承焕生), SHEN HAO (沈皓), TANG JIA-YONG (汤家镛), YANG FU-JIA (杨福家)
Department of Physics Ⅱ, Fudan University, Shanghai 200433, China
Abstract  In this article, we report the 170° backscattering cross sections of 4He from 16O in the energy range of 2.0-9.0 MeV. Our measurements show that the alpha-oxygen scattering remains Rutherford scattering up to E$\alpha$=2.35 MeV, and there exist two energy regions, namely 5.55-5.85MeV and 8.50-8.80MeV, where the cross sections are enhanced and show a smooth variation. The measured laboratory cross sections are 9.50-9.97 and 35.0-33.0 times greater than the Rutherford values, respectively. In the 8.50-8.80MeV region, the cross sections at scattering angles of 160°, 165°, 170° and 175° were measured and found to be strongly angle-dependent. A most strong resonance occurred at 7.60 MeV, where the cross section is 200 times of its Rutherford value. This resonance has been used to measure the 16O concentration on a Cu surface, with a sensitivity of 1×1015 oxygen atoms/cm2, Besides, we have studied the backscattering angle dependence of the threshold energy, i.e., the energy at which the elastic cross section begins to deviate from its Rutherford value. The experimental result seems not in agreement with the prediction made from the analytical formula developed by Bozoian et al.
Received:  05 November 1992      Accepted manuscript online:
 PACS: 61.85.+p (Channeling phenomena (blocking, energy loss, etc.) ?) 68.49.Sf (Ion scattering from surfaces (charge transfer, sputtering, SIMS))
Fund: Project supported by the National Natural Science Foundation of China.