Review of the track models

The string of beads model has been proposed by Samuel and Magee [12] and has been widely used for the discussion of diffusion-controlled reactions in water. Radicals are supposed to be formed in spherical volumes called spurs . About 40 eV energy is deposited in each spur which are equidistant. The distance between spurs is about 3000 A for a 450 eV electron in water. The initial spur radius is 10—15 A. The picture of an electron track according to this model is given in Fig. 4(a). 

The model due to Ganguly and Magee [6] was then proposed to include the slowing down of the primary particle. Each spur corresponds to the same energy deposit but the interspur distance is statistically random (Fig. 1.4(b)). Other models have been reviewed by Mozumder [10]. 

A more refined model was then presented by Mozumder and Magee [11]. It takes into account glancing and knock-on collisions and gives a complete picture of the track. Many new entitites called blobs, short tracks and branch tracks were defined in order to obtain this picture. 

These theories were tentatively used to calculate the yield of free ions 

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