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The light tin isotopes are interesting owing to the vicinity of the doubly-magic $^{100}$Sn, which is the heaviest alpha-conjugate nucleus and has a cluster structure at its low-density surface [1]. The single-particle states outside of this unique core are important for predicting and understanding the structure of nuclei in the region. The ordering of the lowest single-particle states, which are separated by only approximately 200 keV, has yet to be experimentally verified and remains unresolved [2,3].
Our group measured the one-neutron knockout from $^{108}$Sn to establish that the first-excited state of 107Sn has J$^{\pi}$=7/2$^{+}$, strongly suggesting that the ground state has J$^{\pi}$=5/2$^{+}$ [4]. With the increased beam rates at FRIB, the ARIS separator, and Gretina, we were able to measure momentum distributions of the ground and first-excited states of $^{105}$Sn to verify that they have J$^{\pi}$=5/2$^{+}$ and J$^{\pi}$=7/2$^{+}$, respectively [5]. The measured cross sections for these states were compared with shell-model predictions [5]. The lifetimes of the first excited states in $^{103}$Sn, $^{101}$Cd, and $^{103}$Cd were used to extract B(M1) strengths, which were compared with state-of-the-art VS-IMSRG calculations, showing a systematic underprediction [6].
[1] I. Cox et al., Nature 654, 53 (2026).
[2] D. Seweryniak et al., PRL 99, 022504 (2007).
[3] I. Darby et al., PRL 105, 162502 (2010).
[4] G. Cerizza et al., PRC 93, 021601R (2016).
[5] A. Peter, University of Tennessee PhD Dissertation (2026).
[6] T. J. Gray et al., PRC accepted (2026).