ABSTRACT
Theenergyunitofkineticenergydividedbythemassnumberofions,thatis,MeV/u,isvery usefulandwidelyemployedinionbeamresearch,becausethesamevaluegivesthesamevelocity even for a different kind of ion.
13.1.2.1 Physics: Energy Deposition and Appearance of Track Theabove-mentionedapplicationsutilize,moreorless,distinctivefeaturesofheavy-ionbeams inphysics,chemistry,andbiology.Whenafastchargedparticlehasalargeamountofenergy,it depositsitsenergythroughCoulombicinteractionswithmatter.Theseconsistofelectronicand nuclear interactions, which are deŸned as interactions with bond electrons and atomic nuclei in matter,respectively.Forahigh-energyheavyion,theformerinteractionispredominantandresults inejectionofhigh-energysecondaryelectrons.Thesesecondaryelectronsalsodeposittheirenergy throughCoulombicinteractions,andtertiaryelectronsareproduced;however,electronsofallgenerationsproducedintheseprocessesarecollectivelyreferredtoassecondaryelectrons.Energy depositions from both the primary projectile ion and secondary electrons lead to the production of electronsandholesaswellasexcitedmolecules,whichparticipateinconsequentchemicalreactionsandwouldberesponsibleforsubsequentbiologicalresponses.Thus,thepatternsofenergy depositionanddistributionsofchemicalspeciesarerequiredtocomprehendconsequentchemistry, biology,andsoon,andarecalledtrackortrack structure.Inordertocompassthewholepicture of energy deposition processes initiated by the fast heavy ion, cross sections for energy transfer betweensecondaryelectronsandbondelectronsaswellasbetweentheheavyionandelectronsare necessary.Thesecrosssectionshaveintensivelybeeninvestigated,andseveralreviewsonthemand theoriestocorrelatethemtothestoppingpowerhavebeenproposed(seeChapters2through5and 13 (Mozumder, 2004; Toburen, 2004) and references therein).
