RADIOCHEMICAL STUDIES OF NUCLEAR REACTIONS INDUCED BY INTERMEDIATE ENERGY HEAVY IONS.

用放化技术研究了中能重离子引起的核反应，确定了较宽质量数范围内放射性核素的生成截面。用RIKEN环回旋加速器中的^&lt；14&gt；N^&lt；7+&gt；(35和135 Mev/u)和^&lt；40&gt；Ar^&lt；17+&gt；(26和95 Mev/u)离子轰击了Al、V、Cu、Ho和Au薄片。目标通常用铝箔覆盖，以获得“平均后坐距离”。形成的放射性核素用伽马射线能谱仪进行分析。用计算机分析计数数据，得到截面。用各种离子对铜箔进行轰击。鉴定和测定了从^7Be到^&lt；72&gt；As的放射性核素。然而，只有当目标被^&lt；40&gt；Ar^&lt；17+(26 MeV/u)轰击时，才能探测到^&lt；67&gt；Ga等较重的核素。与相同能量的14&gt；N弹丸相比，40&gt；Ar轰击的平均后坐射程较大，且随入射能量的增加而减小。辐照后的金靶的能谱表现出非常复杂的模式。跟踪了几个月的能谱变化，分析了各个伽马射线峰区的衰变曲线。对其他靶子的实验结果的分析正在进行中。

Nuclear reactions induced by intermediate energy heavy ions were studied with radiochemical technique to determine formation cross sections of radionuclides in the wide range of mass numbers. The results are necessary to obtain information on nuclear reaction mechanism as well as production of useful radioisotopes.Thin foils of AI, V, Cu, Ho and Au were bombarded with ^<14>N^<7+>(35 and 135 Mev/u) and ^<40>Ar^<17+>(26 and 95 Mev/u ) ions from the RIKEN Ring Cyclotron. Targets were usually covered with aluminum foils to obtain "mean recoil range". Radionuclides formed were assayed with a gamma-ray spectrometer. The counting data were analyzed with computers to obtain cross sections.The bombardments of copper foils were performed with all types of the ions. Radionuclides from ^7Be to ^<72>As were identified and determined. Heavier nuclides like ^<67>Ga were, however, only detected when the target was bombarded with ^<40>Ar^<17+>( 26MeV/u ). The mean recoil ranges of ^<40>Ar bombardments were larger than those of ^<14>N projectile of nearly the same energies, and they decreased with increase of incident energies.Gamma-ray spectra of the irradiated gold targets showed very complex pattern. The changes of spectra were followed for several months and decay curves of individual gamma-ray peak areas were analyzed. Analyses of the experimental results of the other targets are in progress.