Study of Intermediate-spin States of $^{98}$Y

Abstract

The nuclear structure of the odd-odd nucleus 98 Y has been re-investigated by observing prompt γ rays emitted following the proton-induced fission of a 238 U target, using the JUROGAM-II multidetector array. New highspin decays have been observed and placed in the level schemes using triple coincidences. The experimental level energies and γ-decay patterns are compared to GICM and QPRM calculations, assuming that this neutronrich N = 59 isotone is spherical at low energies and prolate deformed at intermediate spins.

Shape coexistence in the odd-odd nucleus Y98 : The role of the g9/2 neutron extruder

“…We confirm the recent extension [37] of the band on top of the isomer to spin 12 − . The QPRM calculations in Ref.…”

“…The QPRM calculations in Ref. [37] well reproduce the band, when assuming a (π5/2 + [422], ν3/2 − [541]) 4 − configuration for the 496.1-keV isomer, which was also proposed in Refs. [8,52].…”

“…We note that, to date, the highest excitation energy 98 Y observed in fission [37] is at least two times lower than seen in 95 Y [38], 96 Y [39,40] or 97 Y [41]. Considering, that 98 Y is at the maximum of the population in fission of yttrium isotopes, one might expect spherical configurations in this nucleus extending up to 4 MeV.…”

“…We adopt spin-parity 4 − , after Refs. [8,37,52] but stress, that this assignment needs proper, experimental confirmation.…”

“…The GICM [56] calculations done in Ref. [37] partly reproduce such a band of negative-parity, spherical levels. The spin of the 971.3-keV level should be higher than the spin of the 658.4-keV level but lower than I=9, because of no link with the 1181.4-keV isomer.…”