Superdeformation in Asymmetric N$>$Z Nucleus ${}^{40}$Ar

A rotational band with five $\gamma$-ray transitions ranging from 2${}^{+}$ to 12${}^{+}$ states was identified in ${}^{40}$Ar. This band is linked through $\gamma$ transitions from the excited 2${}^{+}$, 4${}^{+}$ and 6${}^{+}$ levels to the low-lying states; this determines the excitation energy and the spin-parity of the band. The deduced transition quadrupole moment of 1.45$^{+0.49}_{-0.31} eb$ indicates that the band has a superdeformed shape. The nature of the band is revealed by cranked Hartree–Fock–Bogoliubov calculations and a multiparticle–multihole configuration is assigned to the band.