Nuclear structure studies in mirror nuclei

International audienceThe nuclear structure of the A=31 and A=47 mirror couples produced by two fusion evaporation reactions has been elaborated, utilizing the Doppler-shift attenuation method. Excited states in $^{31}$P and $^{31}$S were populated using the 1p and 1n exit channels, respectively, of the reaction $^{20}$Ne + $^{12}$C, while in $^{47}$Cr and $^{47}$V couple excited states were populated based on $^{28}$Si + $^{28}$Si reaction, as products of 2αn and 2αp exit channels. The A=31 mirror couple was studied utilizing Piave-Alpi accelerator of the Laboratori Nazionali di Legnaro with GASP multidetector array and for A=47 one - with the EUROBALL array using XTU Tandem also in Legnaro. In both cases the lifetime measurements in mirror couples at the same experiment open possibilities for investigations of isospin symmetry. Determined B(E1) strengths in the mirror nuclei $^{31}$P and $^{31}$S allow to extract the isoscalar component, which can reach up to 24% of the isovector one. The B(E1) values can be modeled by the Equation of motion method. In the case of A=47 mirror couple, the quadrupole moments can be described by shell-model calculations

Examples of dynamic chirality in nuclei

In many cases the chirality was almost observed but the transition probabilities are different. This fact is clearly seen in the cases of 134Pr and 102Rh. In the case of chirality, the yrast and the side bands should be nearly degenerate. In the angular momentum region where chirality sets, the B(E2) values of the electromagnetic transitions deexciting analog states of the chiral twin bands should be almost equal. Correspondingly the B(M1) values should exhibit staggering. Our lifetime measurements in the cases of 134Pr and 102Rh and the theoretical analysis do not support static chirality. Chirality has mainly a dynamical character in both nuclei. In the present paper, we compare our results with the results for other chiral candidate nuclei, which fulfill static chirality conditions

145Ba^{145}\mathrm{Ba} β−{{\beta}}^{{-}} decay: Excited states and half-lives in neutron-rich 145La^{145}\mathrm{La}

International audienceBackground: Neutron-rich nuclei in the A≈140–160 mass region provide valuable information on nuclear structure such as quadrupole- and octupole-shape coexistence and the evolution of the collectivity. These nuclei have also a nuclear engineering interest because they contribute to the total decay heat after a fission burst. The information concerning La145 is very limited.Purpose: The study of low-spin states in La145 will provide a more detailed level scheme and enable the determination of the half-lives of the excited states.Methods: Low-spin excited states in La145 have been investigated from the Ba145β− decay. The Ba145 nuclei were directly produced by photofission in the ALTO facility or obtained from the β− decay of Cs145 also produced by photofission. Gamma spectroscopy and fast-timing techniques were used.Results: A new level scheme was proposed including 67 excited levels up to about 3 MeV and 164 transitions. Half-lives in the few-nanosecond range were measured for the first excited states. Configurations for levels up to ≈600 keV were discussed.Conclusions: The available information on the low-spin states of La145 has been modified and considerably extended. The analysis of the properties of the first excited states, such as excitation energies, decay modes, log ft values, reduced transition probabilities, and Weisskopf hindrance factors, has enabled the identification of the first members of the bands corresponding to the g7/2, d5/2, and h11/2 proton configurations

Examples of dynamic chirality in nuclei

In many cases the chirality was almost observed but the transition probabilities are different. This fact is clearly seen in the cases of 134Pr and 102Rh. In the case of chirality, the yrast and the side bands should be nearly degenerate. In the angular momentum region where chirality sets, the B(E2) values of the electromagnetic transitions deexciting analog states of the chiral twin bands should be almost equal. Correspondingly the B(M1) values should exhibit staggering. Our lifetime measurements in the cases of 134Pr and 102Rh and the theoretical analysis do not support static chirality. Chirality has mainly a dynamical character in both nuclei. In the present paper, we compare our results with the results for other chiral candidate nuclei, which fulfill static chirality conditions

Spectroscopy of the odd-odd chiral candidate nucleus 102Rh

Excited states in 102Rh were populated in the fusion-evaporation reaction 94Zr(11B, 3n)102Rh at a beam energy of 36 MeV, using the INGA spectrometer at IUAC, New Delhi. The angular correlations and the electromagnetic character of some of the 03B3-ray transitions observed in 102Rh were investigated in detail. A new candidate for achiral twin band was identified in 102Rh for the first time

Spectroscopy of the odd-odd chiral candidate nucleus

Excited states in 102Rh were populated in the fusion-evaporation reaction 94Zr(11B, 3n)102Rh at a beam energy of 36 MeV, using the INGA spectrometer at IUAC, New Delhi. The angular correlations and the electromagnetic character of some of the 03B3-ray transitions observed in 102Rh were investigated in detail. A new candidate for achiral twin band was identified in 102Rh for the first time

Symmetries in mirror nuclei 31S and 31P

Excited states in mirror nuclei 31S and 31P were populated in the 1n and 1p exit channels, respectively, of the reaction 20Ne + 12C. The beam of 20Ne, with an energy of 33 MeV, was delivered for the first time by the Piave-Alpi accelerator of the Laboratori Nazionali di Legnaro. Angular correlations of coincident pairs and Doppler-shift attenuation lifetime measurements in 31S and 31P were performed using the multidetector array GASP in conjunction with the EUCLIDES charged particle detector. A comparison of the determined B(E1) strengths of the analog mirror 7/2− → 5/2+ transitions indicates the presence of a violation of isospin symmetry.peerReviewe

Symmetries in mirror nuclei 31S and 31P

Excited states in mirror nuclei 31S and 31P were populated in the 1n and 1p exit channels, respectively, of the reaction 20Ne + 12C. The beam of 20Ne, with an energy of 33 MeV, was delivered for the first time by the Piave-Alpi accelerator of the Laboratori Nazionali di Legnaro. Angular correlations of coincident pairs and Doppler-shift attenuation lifetime measurements in 31S and 31P were performed using the multidetector array GASP in conjunction with the EUCLIDES charged particle detector. A comparison of the determined B(E1) strengths of the analog mirror 7/2- → 5/2+ transitions indicates the presence of a violation of isospin symmetry

Low-lying bands with different quadrupole deformation in

To investigate the interplay between collective and single particle degrees of freedom in odd nuclei, Recoil distance Doppler-shift and Doppler-shift attenuation lifetime measurements were carried out for levels in 155Dy in coincidence detection of gamma-rays. 26 lifetimes were determined using the Differential decay curve method. Particle plus triaxial rotor model (PTRM) calculations were performed to compare the experimental level scheme and transition strengths with theoretical ones in order to get information on the quadrupole deformation (є,γ) of the bands. As a result, different quadrupole deformations for the one-quasineutron bands at low and medium spins are deduced