Nuclear structure studies close to N = Z = 50

Abstract

Abstract. The level structures in 98,99 Rh, and 99 Pd nuclei have been investigated through in beam γ-ray spectroscopic techniques following the 75 As( 28 Si, xpyn) fusion-evaporation reaction at E lab =120 MeV. These investigations were carried out using Indian-National-Gamma-Array (INGA) consisting of Compton-suppressed clover detectors at the Inter-University Accelerator Centre, New Delhi. The level structures observed in 99 Pd, and 98,99 Rh have been established up to ∼11 MeV, 10 MeV and 16 MeV excitation energy and spin∼ 23h, 23h, and 28h respectively. In the doubly-odd 98 Rh nucleus, new band structures and isomeric states have been identified at lower spins and new states below the previously identified 2 + ground state (T 1/2 = 8.5 m) are identified. In the present work 99 Rh structure have been observed similar to 101 Rh which is based on p 1/2 and g 9/2 orbitals. Various positive and negative parity states in these nuclei are observed to be energetically more favored with respect to the neighboring ones, and are likely to be the maximally aligned states obtained by angular momentum coupling of the valence particles (holes). The level structures observed in 99 Pd have been interpreted in the framework of a microscopic theory based on the deformed Hartree-Fock (HF) and angular momentum projection techniques. Band structures at low excitation energy are based on the low-Ω νg 7/2 and νd 5/2 orbitals, have been observed in 99 Pd. Band structure at higher spins are reproduced with the ν(g 7/2 ) 2 ⊗ ν(g 9/2 ) −1 ⊗ ν(h 11/2 ) 2 ⊗ π(g 9/2 ) 6 configurations. Observation of new E1 transitions linking the opposite parity νh 11/2 and νd 5/2 bands provide fingerprints of possible octupole correlations in 99 Pd.The extracted values of the B(E1)/B(E2) ratios for the lower levels in the νh 11/2 band are ∼ 10 −7 [fm] −2 .