Inter-shell zone

The Galactic chemical evolution of heavy neutron-capture elements was studied by Travaglio et al. (1999, 2001) on the assumption that a small pocket of 13C is mixed into the inter-shell zone after the decay of each thermal pulse and generates neutrons supplemented by a small contribution from 22Ne during the next pulse see... 

Figure 6.4 also illustrates a mechanism whereby 13C may be introduced into the inter-shell convection zone of a low- or intermediate-mass star. When that zone reaches its maximum extension, it covers almost the whole inter-shell region apart from a thin interval marked A. The mass of this region decreases from about... 

Figure 6.5 shows a computation of the development of physical conditions during a pulse, according to the old picture. The 13 C source is activated at a relatively low temperature at the moment when the inter-shell convection zone reaches up to the level of the pocket. Later, after exhaustion of 13C, the temperature rises... 

Given that seed nuclei are exposed to a flux of neutrons at T = 1.5 x 108 K, nn = 109 cm-3 for 20 years during a pulse, and r0 = 0.3 mb-1, estimate the overlap fraction r between successive inter-shell convective zones. 

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