β-decay of 113Rh and the observation of 113mPd : Isomer systematics in odd-A palladium isotopes☆

Abstract Decay of 113 Rh to the levels of 113 Pd was studied at the IGISOL-facility by means of β-, γ- and conversion-electron spectroscopy. The level scheme of 113 Pd was constructed using 33 gamma transitions on the basis of observed γγ-coincidence relations and half-life analysis. A β-decay half-life of (2.80±0.12) s was measured for 113 Rh. A new 9 − 2 isomeric state with (0.3 ± 0.1) s half-life and excitation energy 81.3 keV was discovered in 113 Pd. This state and the other recently observed low-lying 9 − 2 or 11 − 2 isomeric states in 115,117 Pd isotopes are directly populated in proton-induced fission. The decay of these isomers is unusually strongly hindered compared with Weisskopf estimates. Our observation of two strongly hindered M2 transitions in 113,117 Pd with hindrance factors of 7600 and 6800, respectively, imply coexistence of nuclear shapes in odd- A Pd nuclei.