Pairing-excitation versus intruder states in 68Ni and 90Zr

TL;DR

This paper compares the nature of 0+ states in 68Ni and 90Zr, highlighting the low-energy proton intruder state in 68Ni and analyzing the shell-model description of these states.

Contribution

It provides new insights into the proton and neutron intruder states in 68Ni and 90Zr, emphasizing the role of pair scattering across N=40.

Findings

Proton intruder state in 68Ni at ~2.2 MeV

Neutron intruder states in 90Zr at 4126 keV and 5441 keV

Shell-model analysis explains low excitation energy in 68Ni

Abstract

A discussion on the nature of the 0+ states in 68Ni (Z=28, N=40) is presented and a comparison is made with its valence counterpart 90Zr (Z=40, N=50). Evidence is given for a 0+ proton intruder state at only ~2.2 MeV excitation energy in 68Ni, while the analogous neutron intruder states in 90Zr reside at 4126 keV and 5441 keV. The application of a shell-model description of 0+ intruder states reveals that many pair-scattered neutrons across N=40 have to be involved to explain the low excitation energy of the proton-intruder configuration in 68Ni.