使用α粒子轰击天然镱靶制备^(178m2)Hf同质异能素及样品γ能谱分析

Isomer^(178m2)Hf prepared by using α particles to bombard a natural ytterbium target and analysis of high purity Ge γ spectrum

178m2Hf是一种长半衰期(T1/2=31 a)、高自旋态(Iπ=16+)的Hf同质异能素.利用四川大学CS-30回旋加速器产生的30 MeV,100μA的α束流轰击天然Yb靶,通过176Yb(α,2n)反应制备178m2Hf.采用高纯Ge探测器测量未提纯样品和放化分离后的样品的γ能谱,选取178m2Hf的426,495和574 keV三个特征峰,使用高斯双峰拟合方法解谱,确定了未提纯样品中178m2Hf的含量达到1012量级,提纯后的样品中178m2Hf含量为1011量级.还对靶中其他放射性杂质核素(175Hf,172Lu,172Hf,177Lu,173Lu)的含量进行了分析.

178m2Hf isomer is of great importance in science and application. Using natural ytterbium bombarded byαparticles to produce 178m2Hf through 176Yb （α, 2n） 178m2Hf nuclear reaction may be a low-cost way. Three natural ytterbium targets of about 200 μm in thickness are fabricated by magnetron sputtering of natural Yb onto copper substrates, and then irradiated with 30 MeV, 50 μA α beam in the CS-30 cyclotron for about 50 hours. After cooling, Hf is isolated from one target through chemical isolation. Gamma spectra of two targets and the isolated Hf sample are measured with high purity Ge detector. Overlapping peaks of the complex spectrum are separated by using Gaussian multi-peak fitting. The content of 178m2Hf nuclide is identified to be 1012 orders of magnitude in each target, and 1011 orders of magnitude in the purified sample from chemical isolation. The content values of other radioactive nuclides （175Hf, 172Lu, 172Hf, 177Lu, 173Lu ） in targets are also measured.