Formation of Elements in Neutron Rich Ejected Matter of Supernovae. II: Dynamical r-Process Stage

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Abstract
Thermal and chemical properties of neutron-rich matter ejected by supernova explosion are investigated along the line of a previous work of the author. In this investigation, the dynamical r-process is worked out for the first time by taking into account a thermodynamical equation. Computations are carried out for a number of sets of expansion speeds and initial n/p ratios at high temperature, and for two extreme cases on fission cutoff, i.e., the pessimistic and optimistic cases on the synthesis of superheavy nuclei. By this investigation the following results are obtained. 1) The energy release accompanied with beta decays and fissions is indispensable in reproducing the observed abundance of the r-process elements. 2) The abundance of the r-process products is almost independent of the initial n/p ratio, but depends on the expansion speed of the supernova. To reproduce the r-process peaks of observed abundances the expansion speed of supernova should be greater than the free fall speed but smaller than thirty times the free fall speed.

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