Thesis, Univ. of Valencia (2020)

A.Tolosa-Delgado

Study of beta-delayed neutron emitters in the region of ⁷⁸Ni and its impact on r-process nucleosynthesis

NUCLEAR REACTIONS ⁹Be(²³⁸U, F)⁷⁵Co/⁷⁶Co/⁷⁵Ni/⁷⁶Ni/⁷⁷Ni/⁷⁸Ni/⁷⁹Ni/⁷⁶Cu/⁷⁷Cu/⁷⁸Cu/⁷⁹Cu/⁸⁰Cu/⁸¹Cu/⁸²Cu/⁷⁹Zn/⁸⁰Zn/⁸¹Zn/⁸²Zn/⁸³Zn/⁸⁴Zn/⁸⁵Zn/⁸²Ga/⁸³Ga/⁸⁴Ga/⁸⁵Ga/⁸⁶Ga/⁸⁷Ga/⁸⁵Ge/⁸⁶Ge/⁸⁷Ge/⁸⁸Ge/⁸⁹Ge/⁹⁰Ge/⁸⁸As/⁸⁹As/⁹⁰As/⁹¹As/⁹²As/⁹¹Se/⁹²Se/⁹³Se/⁹⁴Se/⁹⁴Br/⁹⁵Br, E=345 MeV/nucleon; measured fission fragments using BigRIPS and ZeroDegree spectrometers at RIBF-RIKEN facility for separation of fragments by A/Q and Z through measurements of time-of-flight (TOF), magnetic rigidity (Bρ) and energy loss (ΔE); deduced A/Q versus Z particle identification plots.

RADIOACTIVITY ⁷⁵Co, ^75,76,77,78Ni, ^{76,77,78,79,80,81}Cu, ^{79,80,81,82,83,84}Zn, ^{82,83,84,85,86,87}Ga, ^{85,86,87,88,89}Ge, ^{87,88,89,90,91,92}As, ^91,92,93Se, ^92,94Br(β^-), (β^-n); ^80,81Cu, ^83,84Zn, ^84,85,86,87Ga, ^87,88,89Ge, ^{88,89,90,91,92}As, ⁹³Se(β^-2n);[from ⁹Be(²³⁸U, F), E=345 MeV/nucleon]; measured implanted ions, neutrons, β, γ, β(implants)β-, (implants)β(1n)- and (implants)β(2n)-correlations, T_1/2 of decays of ground states using BRIKEN neutron counter with 140 ³He-filled proportional counters, AIDA array of DSSSDs for implants and β decays, two Clover HPGe detectors for γ radiation, and two thick plastic scintillators; deduced T_1/2, %β^-n or P_n, %β^-2n or P_2n from simultaneous fits of β^-, β^-1n and β^-2n-decay curves, with uncertainties from Monte Carlo method, elemental abundances and effects on r-process nucleosynthesis. Comparison with previous experimental results, and with theoretical calculations in 2019Mo01 (At. Data Nucl. Data Tables 125, 1 (2019)) and 2016Ma12 (Phys. Rev. C 93, 025805 (2016)). Discussed systematics of T_1/2 and P_n values for nuclei in the region of ⁷⁸Ni.