Energy spectra of He+ ions transmitting from thick biological targets

Transmitting energy spectra of 500 keV-1 MeV He+ ions penetrating 50-90 mu m 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 penet rating ions, are inhomogeneous and there are open "channel like"' paths alo ng which the incident ions can transmit the targets easily. While most of t he incident ions are stopped in the targets, some of the transmitting ions only lose a small fraction of their initial incident energy. The transmitti ng energy spectra show a pure electronic stopping feature. Transmission ele ctron microscopic micrograph taken from these samples with thickness of 30 mu m indicate that 150 keV electron beam can penetrate the thick samples to give very good images with clear contrast. The electronic structures of be ta-1 4-glucosan molecular chains, which is deemed as the important constitu ent of the cell walls of seed coats and peels of fruits, are calculated to show the possible channeling directions existing in biological samples.