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

Abstract

High-spin states in the 164 68 Er 96 region were studied using 9 Be + 160 Gd reactions. Pulsed beam conditions were exploited for enhanced sensitivity to delayed γ -ray transitions. New isomers were identified in 161 Dy, 163 Ho, 162 Er, and 165 Er. The 162 Er isomer is interpreted to decay by E1 transitions to the ground-state band with a reduced hindrance of f ν = 33. A plot of f ν values for all K = 7, E1 transitions from two-quasiparticle isomers to the ground-state bands of even-even nuclei reveals only a small influence from the dynamic to kinematic moment-of-inertia ratio, which provides a measure of Coriolis K mixing within the ground-state band. This is interpreted to imply that the relatively low hindrances are due to K mixing in the isomer, caused by a combination of Coriolis and octupole band mixing.

Configurations and hindered decays of K isomers in deformed nuclei with A>100

“…[93], where only 85% of the rigid rotor value was used in estimating the relative excitation energy and more examples were incorporated [93,94] with essentially the same result. As will be the case for any such global evaluation, even with a restriction to specific seniorities, large variations are observed, many of which can be understood through the specific processes already discussed above.…”

Lifetime measurements of Er162 : Evolution of collectivity in the rare-earth region

“…The uncertainty is determined by systematically varying the fit region and background components of the fit. The new lifetime with lower uncertainty changes the reduced hindrance factor for this K isomer from f ν = 33.1(13) [28] to f ν = 32.1(3). Compared to the previous result this indicates a slightly increased degree of Coriolis K mixing of the isomer within the ground-state band [37].…”

“…An isomer with a K π = 7 − assignment at 2027 keV has been observed to decay into the ground state band via 1360 keV and 930 keV transitions [28]. The half-life of the isomer is remeasured by analyzing the HPGe time-stamp distribution of the 1360 keV γ ray decaying into the 6 + 1 state.…”

“…The degree of forbiddenness is described by the reduced hindrance factor f ν [27], where ν = K − λ. In 162 Er, a K π = 7 − isomer decaying to the ground-state band exists with a reduced hindrance of f ν = 33.1 (13) [28]. This state was interpreted as a two-quasiparticle isomer with a π 7/2 − [523]π 7/2 + [404] configuration.…”