1209.5217 (P. G. Bizzeti et al.)

Isospin Symmetry violation in mirror E1 transitions: Coherent
contributions from the Giant Isovector Monopole Resonance in 67As - 67Se    [PDF]

P. G. Bizzeti, G. de Angelis, S. M. Lenzi, R. Orlandi

The assumption of an exact isospin symmetry would imply equal strengths for mirror E1 transitions (at least, in the long-wavelength limit). Actually, large violations of this symmetry rule have been indicated by a number of experimental results, the last of which is the 67As - 67Se doublet investigated at GAMMASPHERE. Here, we examine in detail various possible origins of the observed asymmetry. The coherent effect of Coulomb-induced mixing with the high-lying Giant Isovector Monopole Resonance is proposed as the most probable process to produce a large asymmetry in the E1 transitions, with comparatively small effect on the other properties of the parent and daughter levels.

View original: http://arxiv.org/abs/1209.5217