Deep penetration of charged particles in biological samples

Experimental evidence of abnormally deep penetration in some botanical targ ets by low-energy ion beams is presented. The energy spectra of 818 keV He ions penetrating a 70 mum thick seed coat of maize, fruit peel of grape an d of tomato all have a common feature. The leading edges of these broad spe ctra indicate that some of the penetrating ions pass through the thick targ ets easily and only lose a small ii-action of their initial incident energy . Rutherford backscattering spectrometry and electron microprobe measuremen ts are used to determine the argon concentration in multilayer samples of t he seed coat of maize implanted by 200 keV Ar+ ions. The results show that about 10% of the Ar+ ions can penetrate deeper than similar to 100 mum in t hese samples.