L Ni, Z C Xu, Y Jin, Z H Li, K W Brown, H Hua, S M Wang, C Y Niu, A K Anthony, J Barney, R J Charity, D Dell'Aquila, J M Elson, J Estee, G Jhang, J G Li, W G Lynch, N Michel, L G Sobotka, S Sweany, F C E Teh, A Thomas, C Y Tsang, M B Tsang, H Y Wu, C X Yuan, K Zhu
The ground state of the three-proton emitter ^{17}Na has been identified. Energy correlations between the protons and the ^{14}O residue indicate that its decay is sequential initiated by the emission of a single proton to the ground state of ^{16}Ne followed by simultaneous emission of two protons to the ground state of ^{14}O, and the derived total decay energy is 4.45(3) MeV. The angular distribution of the proton from the first step indicates that this emission is d-wave and only consistent with a spin parity of 5/2^{+}. This assignment is consistent with state-of-the-art Gamow shell-model calculations. As the ground state of ^{17}C is 3/2^{+}, the assigned spin parity of its mirror ^{17}Na indicates that the pair presents a new case of ground-state mirror symmetry violation (GMSV). Unlike other GMSV cases, which arise solely from either a Coulomb induced shift or deformation effects, the ^{17}Na/^{17}C case is generated by differences in the many-body correlations.