Nuclear structure studies close to N = Z = 50

Abstract

The level structures in 98,99Rh, and 99Pd nuclei have been investigated through in beam γ-ray spectroscopic techniques following the 75As(28Si, xpyn) fusion-evaporation reaction at Elab =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 99Pd, and 98,99Rh have been established up to ∼1 MeV, 10 MeV and 16 MeV excitation energy and spin∼ 23ℏ, 23ℏ, and 28ℏ respectively. In the doubly-odd 98Rh nucleus, new band structures and isomeric states have been identified at lower spins and new states below the previously identified 2 + ground state (T1/2 = 8.5 m) are identified. In the present work 99Rh structure have been observed similar to 101Rh which is based on p1/2 and g9/2 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 99Pd 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 vg7/2 and vd5/2 orbitals, have been observed in 99Pd. Band structure at higher spins are reproduced with the v(g7/2)2 ⊗ v(g9/2)-1 ⊗ v(h11/2)2 ⊗ π(g9/2)6 configurations. Observation of new E1 transitions linking the opposite parity vh11/2 and vd5/2 bands provide fingerprints of possible octupole correlations in 99Pd. The extracted values of the B(E1)/B(E2) ratios for the lower levels in the vh11/2 band are ∼ 10-7 [fm]-2. © 2014 AIP Publishing LLC.