Cranking in Isospace - towards a Consistent Mean-field Description of N = Z Nuclei

Excitation spectra ∆ET of T = 0, 1, 2 states in even-even (e-e) and odd-odd (o-o) N = Z nuclei are analyzed within a mean-field based model involving isovector and isoscalar pairing interactions and the iso-cranking formalism applied to restore approximately isospin symmetry. It is shown that T = 0 states in o-o and T = 1 states in e-e nuclei correspond to two-quasiparticle, time-reversal symmetry breaking excitations since their angular momenta are I 6= 0. On the other hand the lowest T = 2 states in ee and T = 1 states in o-o nuclei, which both are similar in structure to their even-even isobaric analogue states, are described as e-e type vaccua excited (iso-cranked) in isospace. It appears that in all cases isoscalar pairing plays a crucial role in restoring the proper value of the inertia parameter in isospace i.e. ∆ET .