Shape coexistence and tilted-axis rotation in neutron-rich hafnium isotopes

We have performed tilted-axis-cranked Hartree-Fock-Bogoliubov calculations for a neutron-rich hafnium isotope ($^{182}$Hf) whose proton and neutron numbers are both in the upper shell region. We study whether the shell effects play a role in producing high-$K$ isomers or highly gamma-deformed states at high spin. In particular, the possibility of shape coexistence and the effect of wobbling motion are discussed.Comment: 4 pages, 3 figures, to be published in Phys. Lett.

Inelastic excitation of new high-spin yrast isomers in 180Ta

For the first time, six-quasiparticle isomers have been observed in the meta-stable nucleus 18073Ta107. Two new high-spin isomers were populated following deep-inelastic reactions with a pulsed 23892U beam incident on a thick 18072Hf target. Out-of-beam γ-ray events were collected using the Gammasphere germanium detector array. In addition to the known four-quasiparticle isomers, yrast Kπ = (22-) and K≥23 six-quasiparticle isomers have been observed with microsecond half-lives. These are the highest-spin isomers observed using the technique of deep-inelastic excitation. The assignments are compared to predictions made by BCS and Lipkin-Nogami multiquasiparticle calculations

Yrast three-quasiparticle K isomers in neutron-rich 181Hf

New high-K orbitals have been identified in the neutron-rich 181Hf nucleus via one-neutron transfer from a pulsed 238U beam onto a stable 180Hf target. Yrast three-quasiparticle high-K isomers, with half-lives as long as 1.5 ms, have been populated. The decay scheme of 181Hf has been extended to (25/2-). Blocked BCS calculations, including residual interactions, compare well with the experimental results

K-hindered decay of a six-quasiparticle isomer in Hf176

The structure and decay properties of high-K isomers in Hf176 have been studied using beam sweeping techniques and the Gammasphere multidetector array. A new ΔK=8 decay branch, from a Kπ=22⊃-, six-quasiparticle, isomeric (t1/2=43μs) state at 4864 keV to the 20⊃- state of a Kπ=14⊃- band, has been identified. The reduced hindrance factor per degree of K forbiddenness for this decay is measured to be unusually low (fν=3.2), which suggests K mixing in the states involved. The deduced interaction matrix elements are discussed within the context of relevant K-mixing scenarios. The 3266-keV state, previously interpreted as a Kπ=16⊃+ intrinsic state, is reassigned as the Jπ=16⊃+ member of the band based on the Kπ=15⊃+ state at 3080 keV. The systematics of fν values as a function of the degree of forbiddenness is discussed in light of this change

The 1,3-Diazabiphenylene system. synthesis, chemistry, and incorporation into a linearly extended purine analogue

117 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984.The first synthesis of the 1,3-diazabiphenylene ring system by cobalt-catalyzed cooligomerization of a novel diethynylpyrimidine and bis(trimethylsilyl)acetylene is described. This diazabiphenylene is found to undergo an unusual structural rearrangement on treatment with acid in methanol, providing a substituted isoquinoline. Progress toward the synthesis of the dimensional probe, lin-bcb-adenine, incorporating the 1,3-diazabiphenylene skeleton, is summarized, and the synthesis of a pyrimido{6,5-i}imidazo{4,5-g}cinnoline, via a heteroaromatic cross coupling reaction, is discussed.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD