Galactic production of 138La: Impact of 138,139La statistical properties

B.V Kheswa,M Wiedeking,F Giacoppo,S Goriely,M Guttormsen,A.C Larsen,F.L Bello Garrote,T.K Eriksen,A Görgen,T.W Hagen,P.E Koehler,M Klintefjord,H.T Nyhus,P Papka,T Renstrøm,S Rose,E Sahin,S Siem,T Tornyi

doi:10.1016/j.physletb.2015.03.065

Abstract

The γ-ray strength functions and nuclear level densities of 138La and 139La have been measured below the neutron separation energies. These new data were used to calculate astrophysical Maxwellian-averaged (n,γ) cross-sections to investigate the production and destruction of the p-nucleus 138La in the photodisintegration process. The results confirm the underproduction of 138La in the p-process with respect to the observed abundances and strongly support the ν-process through νe capture on 138Ba as the main contributor to the synthesis of 138La in Type II supernovae.

Highlights

The major mechanisms to explain the synthesis of nuclei heavier than iron in the universe are: (a) the slow neutron-capture process (s-process), which occurs during the hydrostatic stellar burning phases of low-mass stars during their asymptotic giant branch phase [1] or of massive stars during core He-burning; (b) the rapid neutron-capture process (r-process) taking place in extremely high-neutron density environments [2]
While the light r-process elements up to the first abundance peak might be produced in neutrinodriven outflows of core-collapse supernovae [3,4,5], the decompression of cold neutronized matter from the violent collision of binary neutron stars or a neutron star with companion black holes have been suggested as alternative sites [2,6,7,8]
In this Letter, we report the measurements of the γ -ray strength function (γ SF) and nuclear level density (NLD) in 138La and 139La below separation energy (Sn)

Summary

Introduction

The major mechanisms to explain the synthesis of nuclei heavier than iron in the universe are: (a) the slow neutron-capture process (s-process), which occurs during the hydrostatic stellar burning phases of low-mass stars during their asymptotic giant branch phase [1] or of massive stars during core He-burning; (b) the rapid neutron-capture process (r-process) taking place in extremely high-neutron density environments [2]. While the light r-process elements up to the first (or possibly second) abundance peak might be produced in neutrinodriven outflows of core-collapse supernovae [3,4,5], the decompression of cold neutronized matter from the violent collision of binary neutron stars or a neutron star with companion black holes have been suggested as alternative sites [2,6,7,8]. In particular the 138Ba νe -capture has been calculated to be the largest contributor in the production of 138La [10]

Results

Discussion

Conclusion