Probing the role of proton cross-shell excitations in 70Ni using nucleon knockout reactions

TL;DR

This study investigates the role of proton cross-shell excitations in 70Ni by analyzing knockout reactions, revealing new transitions and providing insights into the configuration of excited states related to nuclear deformation.

Contribution

It introduces new experimental data on 70Ni, including 29 new transitions, and probes the configuration of excited states involving proton excitations across the Z=28 shell closure.

Findings

Identification of specific excited states with proton cross-shell excitations.

Observation of changed population patterns in different knockout reactions.

Reporting of 29 new transitions in 70Ni's level scheme.

Abstract

The neutron-rich Ni isotopes have attracted attention in recent years due to the occurrence of shape or configuration coexistence. We report on the difference in population of excited final states in 70Ni following gamma-ray tagged one-proton, one-neutron, and two-proton knockout from 71Cu, 71Ni, and 72Zn rare-isotope beams, respectively. Using variations observed in the relative transition intensities, signaling the changed population of specific final states in the different reactions, the role of neutron and proton configurations in excited states of 70Ni is probed schematically, with the goal of identifying those that carry, as leading configuration, proton excitations across the Z = 28 shell closure. Such states are suggested in the literature to form a collective structure associated with prolate deformation. Adding to the body of knowledge for 70Ni, 29 new transitions are reported, of which 15 are placed in its level scheme.