生物厚靶的He^+离子透射能谱

ENERGY SPECTRA OF He\++ IONS TRANSMITTING FROM THICK BIOLOGICAL TARGETS 

测量了５００ ｋｅ Ｖ—１ Ｍｅ Ｖ 的 Ｈｅ ＋ 离子穿过５０ —９０ μｍ 厚度的玉米种皮、葡萄果皮和西红柿果皮的透射能谱．结果表明这些生物厚靶是不均匀的，存在着类似于“沟道”的开放通道，沿着这些通道入射离子可以容易地透过靶材料．虽然大多数离子停留在靶中，但一部分透射离子只损失很少的能量．透射能谱显示出一种纯粹的电子阻止特征．３０ μｍ 厚度样品的透射电子显微镜图谱（ Ｔ Ｅ Ｍ） 显示１５０ ｋｅ Ｖ 的电子可以穿过这些样品得到很清晰的图象．β１ ，４ 葡聚糖是生物种皮或果皮细胞壁的重要的组成部分，计算了该分子链的电子结构，指出了生物样品中可能存在的通道方向．

Transmitting energy spectra of 500?keV—1?MeV He\++ ions penetrating 50—90?μm thick seed coat of maize, fruit peel of grape and of tomato are measured. The results indicate that these thick biological targets, as seen by penetrating ions, are inhomogeneous and there are open “channel like” paths along which the incident ions can transmit the targets easily. While most of the incident ions are stopped in the targets, some of the transmitting ions only lose a small fraction of their initial incident energy. The transmitting energy spectra show a pure electronic stopping feature. Transmission electron microscopic micrograph taken from these samples with thickness of 30?μm indicate that 150?keV electron beam can penetrate the thick samples to give very good images with clear contrast. The electronic structures of β\|1,4\|glucosan molecular chains, which is deemed as the important constituent of the cell walls of seed coats and peels of fruits, are calculated to show the possible channeling directions existing in biological samples. PACC: 6180M; 6180J; 8750G