Unveiling the Intruder Deformed 02+ State in 34Si

The 0(2)(+) state in Si-34 has been populated at the GANIL-LISE3 facility through the beta decay of a newly discovered 1(+) isomer in Al-34 of 26(1) ms half-life. The simultaneous detection of e(+)e(-) pairs allowed the determination of the excitation energy E(0(2)(+)) = 2719(3) keV and the half-life T-1/2 = 19.4(7) ns, from which an electric monopole strength of rho(2)(E0) = 13.0(0.9) x 10(-3) was deduced. The 2(1)(+) state is observed to decay both to the 0(1)(+) ground state and to the newly observed 0(2)(+) state [via a 607(2) keV transition] with a ratio R(2(1)(+)) -> 0(1)(+)/2(1)(+) -> 0(2)(+)) = 1380(717). Gathering all information, a weak mixing with the 0(1)(+) and a large deformation parameter of beta = 0.29(4) are found for the 0(2)(+) state, in good agreement with shell model calculations using a new SDPF-U-MIX interaction allowing np-nh excitations across the N = 20 shell gap.