Abstract In this paper, we will briefly review the recent progress on neutron correlations and clustering in neutron-rich nuclei from quasi-free scattering experiments. The quasi-free (p, pn) reaction was measured for Borromean nuclei 11Li, 14Be, and 17B. A surprisingly small s-wave component was found for 17B, revealing a weak neutron halo in 17B, and the comparative study of the three nuclei shows the surface localization of dineutron correlation and its universality in Borromean nuclei. The two-neutron emission of 16Be was also studied, finding strong dineutron correlation in 16Be(g.s.) but weak correlation in 16Be(2+). Two missing-mass measurements using 4He(8He, 8Be) and 8He(p, pα) reactions provided evidence for the 4n resonance, but the 3n resonance was not supported by the recent experiment employing the t(t, 3He)3n charge-exchange reaction. The quasi-free (p, pα) reaction has been extended to unstable nuclei, and the recent experiment unravels the α-2n-α molecule-like cluster structure of 10Be(g.s.).
Yang et al. (2026) studied this question.