New high-spin states of 142 58Ce and 140 56Ba from fusion-fission reactions: Proton excitations in the N = 84 isotones.

High-spin states in the ¹⁴²Ce and ¹⁴⁰Ba nuclei have been populated in the ¹²C + ²³⁸U and ¹⁸O + ²⁰⁸Pb fusion-fission reactions at 90MeV and 85MeV bombarding energy, respectively. The emitted γ -radiation was detected using the Euroball III and IV arrays. The high-spin yrast and near-to-yrast structures of ¹⁴²Ce have been considerably extended. The level scheme of ¹⁴⁰Ba has been extended by six new levels. The newly observed structures in these N = 84 isotones are discussed by analogy with the neighbouring nuclei. [ABSTRACT FROM AUTHOR]