Observation of low-lying resonances in the quasicontinuum of^195,196Pt and enhanced astrophysical reaction rates

Abstract

Abstract. An excess of strength on the low-energy tail of the giant dipole resonance recently has been observed in the γ-decay from the quasicontinuum of 195,196 Pt. The nature of this phenomenon is not yet fully investigated. If this feature is present also in the γ-ray strength of the neutron-rich isotopes, it can affect the neutron-capture reactions involved in the formation of heavy-elements in stellar nucleosynthesis. The experimental level density and γ-ray strength function of 195,196 Pt are presented together with preliminary calculations of the corresponding neutron-capture cross sections.

Low-energy modification of the γ strength function of the odd-even nucleus In115

“…Results on 112 Cd [7] and 116 Sn [8,9] suggest that additional strength could be expected for 115 In at energies between 6 and 10 MeV. In these studies, nuclear level densities and PSFs below the neutron separation energy are extracted from ( 3 He ,αγ ) and ( 3 He , 3 He γ ) reaction data using the Oslo method [11]. Additional dipole strength is introduced on top of the GLO E1 PSF to reproduce the data, in the form of a Gaussian contribution.…”

“…In the context of astrophysical neutron capture rate evaluations, it has been shown that the low-energy part of the PSF can greatly impact stellar rates [1][2][3][4]. Much attention has thus recently been paid to the understanding of additional low-energy resonances in the PSF, observed sitting around the neutron emission threshold energy on the low-energy tail of the giant dipole resonance (GDR).…”

“…Systematic experimental studies on the Cd and Sn isotopic chains have shown PDRs at energies between 6 and 9 MeV for 105,106,111,112 Cd [7], 116−119 Sn [8], 121,122 Sn [9], and 116,124 Sn [10]. The results on Cd, 116−119 Sn and 121,122 Sn are obtained from ( 3 He , 3 He γ ) and ( 3 He ,αγ ) reactions using the Oslo method [11], whereas the results on 116,124 Sn are obtained from high-resolution nuclear resonance fluorescence (NRF) data. The latter allow the determination of absolute values of the PSF at energies below the neutron emission threshold.…”