Discovery of a nonyrast Kπ=8+ isomer in Dy162, and the influence of competing K-mixing mechanisms on its highly forbidden decay

The Gd160(Be9,α3n)Dy162 reaction has been used to study high-spin states in Dy162. Pulsed beam conditions were utilized for enhanced isomer sensitivity. An isomer at 2188.1(3) keV with a half-life of 8.3(3) μs has been discovered and assigned Kπ= 8+ with a two-quasineutron configuration. Among 11 γ-ray decay branches, an E2, ΔK=8 transition to the ground-state band was observed with a reduced hindrance of fν=35, agreeing well with systematics correlating fν with the product of the valence neutron and proton numbers (NpNn) over an extended N,Z range. Small deviations from NpNn dependence are analyzed for a range of two-quasiparticle isomer decays and interpreted as arising from a weak dependence on the isomer excitation energy relative to the yrast line

Discovery of isomers in dysprosium, holmium, and erbium isotopes with N = 94 to 97

High-spin states in the 68164Er96 region were studied using 9Be + 160Gd reactions. Pulsed beam conditions were exploited for enhanced sensitivity to delayed γ-ray transitions. New isomers were identified in 161Dy, 163Ho, 162Er, and 165Er. The 162Er isom

New structures in 178Hf and coulomb excitation of isomers

A 985 MeV 178Hf beam was Coulomb excited by a 208Pb target at the ATLAS accelerator of Argonne National Laboratory. Gammasphere and the CHICO particle detector recorded particle-γ coincidence data. The aim was to populate and determine the mechanism of previously observed Coulomb excitation of the Kπ = 6+ (t1/2 = 77 ns), 8- (4 s) and 16+ (31 y) isomer bands. New rotational bands were identified including an aligned band which appears to mix with the ground-state band (GSB) and the γ-vibrational band above ∼ 12 ℏ of angular momentum. Newly observed γ-decay transitions into the three isomer bands may elucidate the K-mixing which allows Coulomb excitation of these isomer bands, but direct decays from the GSB into the 16+ isomer band have not yet been confirmed

Technique for Resolving Low-lying Isomers in the Experimental Storage Ring (ESR) and the Occurrence of an Isomeric State in 192Re

A recent experiment using projectile fragmentation of a 197Au beam on a 9Be target, combined with the fragment recoil separator and experimental storage ring at ring at GSI, has uncovered an isomeric state in 192Re at 267(10) keV with a half-life of ∼6

Hindered decays from a non-yrast four-quasiparticle isomer in 164 Er

The half-life of a Kπ=12+ isomer in 164Er has been measured to be 68(2) ns, and new decay pathways have been identified. These include highly K-forbidden γ-ray transitions directly to the ground-state rotational band, with reduced hindrance values tha

Isomers in neutron-rich lead isotopes populated via the fragmentation of 238U at 1 GeV A

Neutron-rich nuclei beyond N = 126 in the lead region were populated by fragmenting a238U beam at 1 GeV A on a Be target and then separated by the Fragment Separator (FRS) at GSI. Their isomeric decays were observed, enabling study of the shell structur

Discovery of Highly Excited Long-Lived Isomers in Neutron-Rich Hafnium and Tantalum Isotopes through Direct Mass Measurements

A study of cooled Au197 projectile-fragmentation products has been performed with a storage ring. This has enabled metastable nuclear excitations with energies up to 3 MeV, and half-lives extending to minutes or longer, to be identified in the neutron-rich nuclides Hf183,184,186 and Ta186,187. The results support the prediction of a strongly favored isomer region near neutron number 116

Long-lived isomers in neutron-rich Z=72 76 nuclides

A study of neutron-rich isotopes in the A=185 region of the nuclear chart has uncovered long-lived (>1s) isomers in several isotopes of hafnium, tantalum, tungsten, rhenium, and osmium. The region was accessed via the use of projectile fragmentation wit