arXiv subjects

A. Mitu

Publications and source records attributed to A. Mitu.

4 recordsLinked to original sources

arXiv2026

Sizeable mixing between the coexisting normal and intruder structures of $^{96}$Zr revealed through lifetime measurements

Lifetimes of excited states of the nucleus $^{96}$Zr were studied with the Doppler-shift attenuation method following the $^{94}$Zr($^{18}$O,$^{16}$O)$^{96}$Zr two-neutron transfer reaction. The obtained $B(E2;2^+_2\to0^+_2)$ and $B(E2;4^+_1\to2^+_2)$ transition strengths, amounting to $26(2)$ and $39(7)$\,W.u., respectively, firmly attribute the $2^+_2$ and $4^+_1$ states to the collective intruder band built on top of the $0^+_2$ state. The nature of this structure is discussed against predictions of the collective model using the Bohr Hamiltonian, the interacting boson model with configuration mixing, and the quasiparticle vacua shell model. The collective, interband $B(E2;4^+_1\to2^+_1)=11.2(8)$\,W.u. transition strength, refuting the previously assumed purity of both structures, is reproduced in the calculations. The quasiparticle vacua shell model predicts, in agreement with a simple two-state model based on experimental $E2$ transition strengths, considerable mixing between the normal and intruder $2^+$ states.

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arXiv2025

Lifetimes of the $2^+_1$ and $4^+_1$ states of the neutron-rich nuclide $^{200}$Pt

The lifetimes of the $2^+_1$ and $4^+_1$ states of $^{200}$Pt were measured applying the recoil-distance Doppler-shift method. Excited states were populated in the $^{198}$Pt($^{18}$O, $^{16}$O)$^{200}$Pt two-neutron transfer reaction at the $9\,\text{MV}$ tandem accelerator at the IFIN-HH in Măgurele, Romania. The resulting $B(E2)$ values of the $2^+_1 \rightarrow 0^+_1$ and $4^+_1 \rightarrow 2^+_1$ transitions as well as the $B_{4/2}$ ratio of $2.08(32)$ indicate the nuclear structure evolving towards sphericity when approaching the neutron shell closure at $N = 126$. The $B(E2; 2^+_1 \rightarrow 0^+_1)$ values of Pt and Hg are compared to values of Te, Xe and Ba as both regions of the nuclear chart show similar structural effects.

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arXiv2022

On the multipole mixing ratio of the $1066$ keV transition from the 0.52 $μs$ isomer of $^{180}$Hf

The nucleus $^{180}$Hf is one of the most primary of examples of an axially symmetric prolate rotor. Combined with the presence of high-$K$ isomers, spectroscopic studies can provide important information on the nature of its single-particle levels. Precise measurements are essential for constraining nuclear models and interpreting the nature of such isomeric states. In this work, the nucleus $^{180}$Hf was populated using the proton pick-up reaction $^{181}$Ta($^{11}$B,$^{12}$C)$^{180}$Hf at beam energy of 47 MeV at Horia Hulubei National Institute of Nuclear Physics and Engineering (IFIN-HH). The spin of the 1374 keV state and the mixing ratio of the $1066$ keV transition have been measured, the latter with an increased precision compared to the previous value from literature. The presently measured spin of the 1374 keV state, currently assigned a tentative value of $(4^-_1)$, favors one of the two different values reported in the literature. The particular state constitutes the band-head of a rotational band in $^{180}$Hf. The measured multipolarity mixing ratio of the inter-band transition $1374 \rightarrow 309$ keV can provide important information for the testing and constraining of theoretical nuclear models used for the study of the intrinsic properties of $^{180}$Hf as well as its neighboring isotopes.

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arXiv2020

Shape Coexistence at Zero Spin in 64Ni Driven by the Monopole Tensor Interaction

The low-spin structure of the semimagic 64Ni nucleus has been considerably expanded: combining four experiments, several 0+ and 2+ excited states were identified below 4.5 MeV, and their properties established. The Monte Carlo shell model accounts for the results and unveils an unexpectedly complex landscape of coexisting shapes: a prolate 0+ excitation is located at a surprisingly high energy (3463 keV), with a collective 2+ state 286 keV above it, the first such observation in Ni isotopes. The evolution in excitation energy of the prolate minimum across the neutron N = 40 subshell gap highlights the impact of the monopole interaction and its variation in strength with N.

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