Parity violation in the γ-decay of polarized 93 Tc nuclei in the 17 2 − isomeric state

We report on a determination of the parity nonconserving (PNC) matrix element in the bound parity doublet 17−2 − 17+2 of 93Tc. The experiment was carried out at the GSI, Darmstadt and LNL, Legnaro laboratories. The recoil-mass-separated radioactive beam of 93Tc nuclei in the 17−2 isomer, following a fusion-evaporation reaction, was polarized by the tilted-foil method and the resulting 0°–180° γ asymmetry with respect to the induced polarization direction was measured by two large-volume Ge detectors. The measured γ asymmetry of 3-σ significance, Aγ = 8.4(2.7) · 10−4, yields a matrix element of |〈17−2|Hpnc|17+2〉| = 0.59(19)(25) meV. This experimental result is c microscopic calculations based on the DDH "best value" interaction for the nuclear weak Hamiltonian. We discuss our results and their significance with respect to the existing data regarding PNC effects in bound nuclear systems