Shape Coexistence in

Large-scale shell-model calculations predict that the region of deformation which comprises the heaviest chromium and iron isotopes at and beyond N=40 will merge with a new one at N=50 in an astonishing parallel to the N=20 and N=28 case in the neon and magnesium isotopes. We propose a valence space including the full pf shell for the protons and the full sdg shell for the neutrons, which represents a comeback of the the harmonic oscillator shells in the very neutron- rich regime. The onset of deformation is understood in the framework of the algebraic SU(3)-like structures linked to quadrupole dominance. Our calculations preserve the doubly magic nature of the ground state of ^{78}Ni, which, however, exhibits a well-deformed prolate band at low excitation energy, providing a striking example of shape coexistence far from stability. This new IOI adds to the four well-documented ones at N=8, 20, 28, and 40.

Superdeformed and Triaxial States in

Shape parameters of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in ^{42}Ca were determined from E2 matrix elements measured in the first low-energy Coulomb excitation experiment performed with AGATA. The picture of two coexisting structures is well reproduced by new state-of-the-art large-scale shell model and beyond-mean-field calculations. Experimental evidence for superdeformation of the band built on 0_{2}^{+} has been obtained and the role of triaxiality in the A∼40 mass region is discussed. Furthermore, the potential of Coulomb excitation as a tool to study superdeformation has been demonstrated for the first time.