Single-particle strength toward N = 32: Spectroscopy of 51 Ca via the 50 Ca(d, p) reaction

TL;DR

This study investigates the single-particle structure of neutron-rich 51 Ca using transfer reactions, providing new experimental data that supports shell model predictions and enhances understanding of shell evolution near N=32.

Contribution

It presents the first spectroscopic data for 51 Ca via the 50 Ca(d, p) reaction, comparing results with advanced theoretical models to clarify single-particle states.

Findings

Identification of 1/2- and 5/2- states in 51 Ca

Evidence for a 9/2+ state consistent with neutron excitation into 0g9/2

Spectroscopic factors supporting shell-model predictions

Abstract

States in the neutron-rich isotope 51 Ca were populated via the 50 Ca(d, p) transfer reaction in inverse kinematics at a beam energy of about 14 AMeV. The experiment was performed using a decelerated radioactive 50 Ca beam from the OEDO facility and the TiNA2 silicon array in combination with the SHARAQ magnetic spectrometer at RIBF/RIKEN. The energies of excited states in 51 Ca were reconstructed via missing mass spectroscopy, and angular distributions of protons were measured to extract differential cross sections. From a comparison with adiabatic distorted wave approximation (ADWA) calculations, spectroscopic factors were deduced for several states, including the ground state and excited states up to 4.2 MeV. These results are compared with shell-model calculations, as well as ab initio valence-space in-medium similarity renormalization group (VS-IMSRG) predictions. The data support the assignment of the 1/2- and 5/2- single-particle states and provide evidence for a candidate 9/2+ state with a structure consistent with neutron excitation into the 0g9/2 orbital. These findings contribute new constraints on the single-particle structure and shell evolution in neutron-rich calcium isotopes.