Badanie korelacji kątowych kwantów gamma za pomocą układu EAGLE

W pracy przedstawiono wyniki analizy danych z eksperymentów, w których metodą korelacji kątowych badano jądra 130Ba, 140Sm i 124Cs wyprodukowane z użyciem wiązek ciężkich jonów dostarczonych przez cyklotron U-200P należący do Środowiskowego Laboratorium Ciężkich Jonów UW. W pomiarach wykorzystano wielodetektorowy spektrometr promieniowania γ - EAGLE. Badania przyniosły następujące rezultaty: • w pasmach chiralnych jądra 124Cs wyznaczono udział promieniowania typu M1 w przejściach pomiędzy stanami, dla których ΔI = 1. Wyniki porównano z przewidywaniami teoretycznymi. Wyniki zgadzają się jakościowo z przewidywaniami teorii. Nowe informacje uzyskane z pomiaru korelacji kątowych umożliwiły wyznaczenie zredukowanych prawdopodobieństw przejść w jądrze 124Cs, • w jądrze 130Ba określono stosunek zmieszania δ (E3/M2), dla przejścia gamma pomiędzy stanem izomerycznym o spinie I = 8− i K = 8 a stanem 6+ należącym do pasma zbudowanego na stanie podstawowym, • w jądrze 140Sm wyznaczono spin I = 2 dla stanu o energii 990 keV (zamiast sugerowanych w poprzednich pracach I = 0+) oraz spin I = 0 dla stanu o energii 1599,1 keV (zamiast sugerowanych w poprzednich pracach I = 2+). Nowe informacje uzyskane z pomiaru korelacji kątowych w przypadku 140Sm umożliwiły analizę pomiarów wzbudzeń kulombowskich. • Sformułowano szereg procedur analizy danych oraz zdefiniowano warunki do przeprowadzenia eksperymentu korelacji kątowych. Wyniki analizy danych dotyczących jądra 124Cs i 140Sm zostały już opublikowane

Quadrupole deformation of Xe-130 measured in a Coulomb-excitation experiment

Low-lying states in the isotope Xe-130 were populated in a Coulomb-excitation experiment performed at CERN's HIE-ISOLDE facility. The magnitudes and relative signs of seven E2 matrix elements and one M1 matrix element coupling five low-lying states in Xe-130 were determined using the semiclassical coupled-channel Coulomb-excitation least-squares search code GOSIA. The diagonal E2 matrix elements of both the 2(1)(+) and 4(1)(+) states were extracted for the first time. The reduced transition strengths are in line with those obtained from previous measurements. Experimental results were compared with the general Bohr Hamiltonian with the microscopic input from mean-field theory utilizing universal nuclear energy density functional (UNEDF0), shell-model calculations using the GCN50:82 and SN100PN interactions, and simple phenomenological models (Davydov-Filippov and gamma-soft). The extracted shape parameters indicate triaxial-prolate deformation in the ground-state band. In general, good agreement between theoretical predictions and experimental values was found, while neither phenomenological model was found to provide an adequate description of Xe-130.Peer reviewe

Nuclear Structure Study of 104^{104}Pd by Coulomb Excitation at the Warsaw Heavy Ion Laboratory

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Decay of the I π = 8 − isomeric state in Nd 134 and Pt 184 studied by electron and γ spectroscopy

International audienceThe properties of the K-isomer decays in the 134 Nd and 184 Pt nuclei have been investigated. Measurements were carried out in e-γ and γ-γ coincidence modes using electron spectrometers coupled to the central European Array for Gamma Levels Evaluations at the Heavy Ion Laboratory of the University of Warsaw. Internal conversion coefficients were obtained for transitions relevant to the decay of the isomeric states, allowing the determination of multipolarities and mixing ratios as well as hindrance factors. Two possible causes of the weakening of the K forbiddenness, namely rotational K mixing (Coriolis interaction) and triaxiality, are briefly discussed using schematic theoretical models

Revised spin values of the 991 keV and 1599 keV levels in 140Sm

The previously accepted spin values of the 991 and 1599 keV levels in Sm140 have been revised and established as 2+ and 0(+), respectively. The γ−γ angular correlation method was used to determine the new spin values. The excited low-spin levels in Sm140 were populated in the Eu140→140Sm and Gd140→ Eu140→140Sm decays. The Gd140 and Eu140 nuclei were produced in the Cd112+S32 reaction at a beam energy of 155 MeV. © 2015 American Physical Societ

Lifetime of the recently identified 10+^+ isomeric state at 3279 keV in the 136^{136}Nd nucleus

International audienceBackground: The γ softness of Nd136 makes it possible to study the shape changes induced by two-proton or two-neutron excitation. Purpose: We measure the lifetimes of two-quasiparticle states of the bands based on the 10+ states at 3296 and 3279 keV to investigate the shape change induced by the alignment of two protons or two neutrons in the h11/2 orbital. Methods: The recoil-distance Doppler shift method was used for the study of Nd136 studies, which was formed by the fusion reaction Sn120(Ne20,4n)Nd136, at Ebeam=85 MeV. Calculations were performed within the microscopic-macroscopic approach, based on the deformed Woods-Saxon single-particle potential and the Yukawa-plus-exponential macroscopic energy. Results: The lifetime of the 10+ state at 3279 keV of Nd136 was measured to be T1/210+=1.63(9) ns. The lifetimes of the 2+ state at 374 keV and of the 12+ state at 3686 keV of the ground band were also measured to be T1/22+=26.5(14) ps and T1/212+=22.5(14) ps. Conclusions: The measured lifetime of 10+ the state at 3279 keV together with other observables confirm the structure change in Nd136. A rather small reduced hindrance of the electromagnetic decay of the 10+ state at 3279 keV would be consistent with its K-mixed character

Multi-step Coulomb excitation of 132Ba at HIL, Warsaw

599-601To determine the shape of 132Ba Coulomb excitation measurement has been performed at U-200P cyclotron at Heavy Ion Laboratory, University of Warsaw, Poland. A 32S beam of ~90 MeV energy has been bombarded on enriched 132Ba-target to Coulomb excite the latter nuclei. EAGLE gamma-ray spectrometer consisting of 15 single crystal HPGe detectors has been used to detect the deexcited gamma-rays from Coulomb excited Ba nuclei. The data has been collected using Particle-gamma coincidence technique for a period of seven days. The back scattered projectiles have been identified with 48 PiN diodes of 0.5 X 0.5 cm2 active area mounted in a scattering chamber of ~5 cm radius called as ‘Munich chamber’. The energy states up to ~1127 keV energy have been populated in the interested 132Ba isotope. The preliminary results of the data analysis are presented here