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تسجيل مستخدم جديدShell evolution of $N=40$ isotones towards $^{60}$Ca: First spectroscopy of $^{62}$Ti
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Excited states in the $N=40$ isotone $^{62}$Ti were populated via the $^{63}$V$(p,2p)$$^{62}$Ti reaction at $sim$200~MeV/u at the Radioactive Isotope Beam Factory and studied using $gamma$-ray spectroscopy. The energies of the $2^+_1 rightarrow 0^{+}_{mathrm{gs}}$ and $4^+_1 rightarrow 2^+_1$ transitions, observed here for the first time, indicate a deformed $^{62}$Ti ground state. These energies are increased compared to the neighboring $^{64}$Cr and $^{66}$Fe isotones, suggesting a small decrease of quadrupole collectivity. The present measurement is well reproduced by large-scale shell-model calculations based on effective interactions, while ab initio and beyond mean-field calculations do not yet reproduce our findings. The shell-model calculations for $^{62}$Ti show a dominant configuration with four neutrons excited across the $N=40$ gap. Likewise, they indicate that the $N=40$ island of inversion extends down to $Z=20$, disfavoring a possible doubly magic character of the elusive $^{60}$Ca.
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