Neutron Knockout on Beams of $^{108,106}$Sn and $^{106}$Cd

Abstract

Characterizing the nature of single-particle states outside of double shell closures is essential to a fundamental understanding of nuclear structure. This is especially true for those doubly magic nuclei that lie far from stability and where the shell closures influence nucleo-synthetic pathways. The region around $^{100}$Sn is one of the most important due to the proximity of the N=Z=50 magic numbers, the proton-drip line, and the end of the rp-process. However, owing to the low production rates, there is a lack of spectroscopic information and no firm spin-parity assignment for ground states of odd-A isotopes close to $^{100}$Sn. Neutron knockout reaction experiments on beams of $^{108,106}$Sn and $^{106}$Cd have been performed at the NSCL. By measuring gamma rays and momentum distributions from reaction residues, the spin of ground state and first excited state for $^{107,105}$Sn have been established. The results also show a degree of mixing in the ground states of the isotopes $^{108,106}$Sn between the d$_{5/2}$ and g$_{7/2}$ single particle-states and they are compared to reaction calculations. Single-, double-, and triple-neutron knockout reactions on the $^{106}$Cd beam have been observed. The spin-parity of $^{105}$Cd is already known, therefore, the measurement of the momentum distributions of the ground and first excited states of this residue is an important validation of the technique used for the light tin isotopes.