Synthesis and Reanalysis of Light Short-lived Actinides

W.q Zhang ,J G Wang ,L J Sun ,Z Y Zhang ,X Y Liu ,Long Ma ,J Li ,Z H Li ,C J Lin ,H S Xu ,T H Huang ,Bing Ding ,Mingguang Sun ,G Q Xiao ,Z G Gan ,Lingfei Yu ,K L Wang ,X Wang ,Zheng-Wei Liu ,Wei Zuo ,Y S Wang ,M L Liu ,H B Yang ,N R ,X H Zhou ,Haiyan Lu ,Chong Qi ,F S Zhang

doi:10.7566/jpscp.32.010025

Abstract

Short-lived \(\alpha \) emitters with N = 128–131 and Z = 91–93 were studied in the fusion reaction ^40Ar + ^187Re using the digital pulse processing technique at the gas-filled recoil separator Spectrometer for Heavy Atom and Nuclear Structure (SHANS). Two new isotopes ^223,224Np were identified and the decay of 220 Pa was re-investigated through temporal and spatial correlations. The pileup signals were resolved by using the digital pulse processing technique. An \(\alpha \) decay with half-life of \(T_{1/2} = 2.15(_{52}^{100})\) μs and energy of \(E_{\alpha } = 9477(44)\) keV was attributed to ^223Np. Two \(\alpha \)-decay branches with half-life of \(T_{1/2} = 38(_{11}^{26})\) μs, \(\alpha \) energies of 9137(21) and 8868(60) keV were assigned to ^224Np, decaying to two excited states in ^220Pa. The results of ^223Np disprove the existence of a Z = 92 subshell closure.

Highlights

The evolution of proton shell structure beyond 208 Pb is of decisive importance for the shell stabilization of superheavy elements
This is at variance with large-scale shell-model calculations [6], which show no sign of a shell gap at Z = 92 for N = 126 isotones and are in overall agreement with spectroscopic data on these isotones up to U [6,7,8,9,10]
In order to identify decay chains belonging to 223 Np, all digital traces correlated to the subsequent α decay of 215 Ac (Eα = 7600(4) keV, T1/2 = 0.17(1) s) [25], which are the third members of the α-decay chain originating from 223 Np, were checked event by event for the presence of multiple pulses

Summary

Introduction

The evolution of proton shell structure beyond 208 Pb is of decisive importance for the shell stabilization of superheavy elements. 52 ) μs and energy of Eα = 9477(44) keV was attributed to 223 Np. Two α-decay branches with half-life of T1/2 = 38(26 The proton separation energy, ground-state spin and parity of odd-Z isotopes beyond

Results

Conclusion