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Register a new userHigh-K isomer and the rotational properties in the odd-Z neutron-rich nucleus $^{163}$Eu
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The newly observed isomer and ground-state band in the odd-Z neutron-rich rare-earth nucleus $^{163}$Eu are investigated by using the cranked shell model (CSM) with pairing treated by the particle-number conserving (PNC) method. This is the first time detailed theoretical investigations are performed of the observed $964(1)$ keV isomer and ground-state rotational band in $^{163}$Eu. The experimental data are reproduced very well by the theoretical results. The configuration of the $964(1)$ keV isomer is assigned as the three-particle state $frac{13}{2}^{-}( ufrac{7}{2}^{+}[633]otimes ufrac{1}{2}^{-}[521]otimespifrac{5}{2}^{+}[413]$). More low-lying multi-particle states are predicted in $^{163}$Eu. Due to its significant effect on the nuclear mean field, the high-order $varepsilon_{6}$ deformation plays an important role in the energy and configuration assignment of the multi-particle states. Compared to its neighboring even-even nuclei $^{162}$Sm and $^{164}$Gd, there is a $10%sim15%$ increase of $J^{(1)}$ of the one-particle ground-state band in $^{163}$Eu. This is explained by the pairing reduction due to the blocking of the nucleon on the proton $pifrac{5}{2}^{+}$[413] orbital in $^{163}$Eu.
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The rotational bands in the neutron-rich nuclei $^{153-157}$Pm are investigated by a particle-number conserving method. The kinematic moments of inertia for the 1-quasiparticle bands in odd-$A$ Pm isotopes $^{153, 155, 157}$Pm are reproduced quite well by the present calculation. By comparison between the experimental and calculated moments of inertia for the three 2-quasiparticle bands in the odd-odd nuclei $^{154, 156}$Pm, their configurations and bandhead spins have been assigned properly. For the 2-quasiparticle band in $^{154}$Pm, the configuration is assigned as $pi5/2^-[532]otimes u3/2^-[521]$ ($K^pi=4^+$) with the bandhead spin $I_0=4hbar$. In $^{156}$Pm, the same configuration and bandhead spin assignments have been made for the 2-quasiparticle band with lower excitation energy. The configuration $pi5/2^+[413]otimes u5/2^+[642]$ ($K^pi=5^+$) with the bandhead spin $I_0=5hbar$ is assigned for that with higher excitation energy.
Experimentally observed ground state band based on the $1/2^{-}[521]$ Nilsson state and the first exited band based on the $7/2^{-}[514]$ Nilsson state in the odd-$Z$ nucleus $^{255}$Lr are studied by the cranked shell model (CSM) with the paring correlations treated by the particle-number-conserving (PNC) method. This is the first time the detailed theoretical investigations being performed on these rotational bands. Both the experimental kinematic and dynamic moment of inertia ($mathcal{J}^{(1)}$ and $mathcal{J}^{(2)}$) versus rotational frequency are reproduced quite well by the PNC-CSM calculations. By comparing the theoretical kinematic moment of inertia $mathcal{J}^{(1)}$ with the experimental ones extracted from different spin assignments, the spin $17/2^{-}rightarrow13/2^{-}$ is assigned to the lowest-lying $196.6(5)$ keV transition of the $1/2^{-}[521]$ band, and $15/2^{-}rightarrow11/2^{-}$ to the $189(1)$ keV transition of the $7/2^{-}[514]$ band, respectively. The proton $N=7$ major shell is included in the calculations. The intruder of the high$-j$ low$-Omega$ orbitals $1j_{15/2}$ $ (1/2^{-}[770])$ at the high spin leads to the band-crossing at $hbaromegaapprox0.20$ ($hbaromegaapprox0.25$) MeV for the $7/2^{-}[514]$ $alpha=-1/2$ ($alpha=+1/2$) band, and at $hbaromegaapprox0.175$ MeV for the $1/2^{-}[521]$ $alpha=-1/2$ band, respectively. Further investigations show that the band-crossing frequencies are quadrupole deformation dependent.
We investigate the influence of deformation on the possible occurrence of long-lived $K$ isomers in Hf isotopes around N=116, using configuration-constrained calculations of potential-energy surfaces. Despite having reduced shape elongation, the multi-quasiparticle states in $^{186,188}$Hf remain moderately robust against triaxial distortion, supporting the long expected occurrence of exceptionally long-lived isomers. The calculations are compared with available experimental data.
The neutron rich nucleus $^{193}$Os was produced in the $^{192}$Os($^{7}$Li,$^{6}$Li)$^{193}$Os reaction. An isomeric state based on the $9/2^-$[505] nilsson orbital was identified in the present work. Half-life of the isomeric state was extracted and discussed in terms of the $K$ quantum number. Level scheme built on the isomeric state was proposed based on the experimental data.
The structure of the nucleus 25F was investigated through in-beam {gamma}-ray spectroscopy of the fragmentation of 26Ne and 27,28Na ion beams. Based on the particle-{gamma} and particle-{gamma}{gamma} coincidence data, a level scheme was constructed and compared with shell model and coupled-cluster calculations. Some of the observed states were interpreted as quasi single-particle states built on top of the closed-shell nucleus 24O, while the others were described as states arising from coupling of a single proton to the 2+ core excitation of 24O.
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