We study static non-axial octupole deformations in proton-rich $Z=N$ nuclei, $^{ 64}$Ge, $^{ 68}$Se, $^{ 72}$Kr, $^{ 76}$Sr, $^{ 80}$Zr and $^{ 84}$Mo, by using the Skyrme Hartree-Fock plus BCS calculation with no restrictions on the nuclear shape. The calculation predicts that the oblate ground state in $^{ 68}$Se is extremely soft for the $Y_{ 33}$ triangular deformation, and that in $^{ 80}$Zr the low-lying local minimum state coexisting with the prolate ground state has the $Y_{ 32}$ tetrahedral deformation.
Categories: nucl-th