Lifetime measurements of the low-lying excited states of ²⁰⁸Po

In this study we present the preliminary results about the lifetimes of the 2₂⁺, 4₁⁺ states of ²⁰⁸Po and the upper limit of the lifetime of the 2₁⁺ state. For measuring the lifetimes of the 2₁⁺ and 4₁⁺ states the Recoil Distance Doppler Shift (RDDS) method and for the lifetime of the 2₂⁺ state the Doppler Shift Attenuation method (DSAM) were used. The resulting absolute transition strength B(M1 ; 2₂⁺ → 2₁⁺) ≥ 0.122(20) μN² reveals the predominant isovector nature of the 2₂⁺ state of ²⁰⁸Po

Lifetime measurements of Er-162: Evolution of collectivity in the rare-earth region

Lifetimes of low-lying yrast states in Er-162 are measured using the electronic gamma-gamma fast-timing technique. Excited states were populated in a Sm-154(C-12, (4)n)Er-162 fusion-evaporation reaction and gamma rays were detected in a combined setup of high purity germanium and LaBr3(Ce) scintillation detectors. The lifetimes of the 4(1)(+) and 6(1)(+) states are determined for the first time and the lifetimes of the 2(1)(+) and 7- states are remeasured with higher precision. Reduced transition probabilities are extracted and well reproduced by theoretical calculations in the framework of the confined beta soft model and the interacting boson model

Tests of collectivity in Zr-98 by absolute transition rates

Lifetimes of low-spin excited states in Zr-98 were measured using the recoil-distance Doppler-shift technique , and the Doppler-shift attenuation method. The nucleus of interest was populated in a( 96)zr(O-18, O-16) Zr-98 two- neutron transfer reaction at the Cologne FN Tandem accelerator. Lifetimes of six low-spin excited states, of which four are unknown, were measured. The deduced B(E2) values were compared with Monte Carlo shell model and interacting boson model with configuration mixing calculations. Both approaches reproduce well most of the data but leave challenging questions regarding the structure of some low-lying states

Search for mixed-symmetry states in 212^{212}Po

International audienceIn this work we present an experiment dedicated to searching for quarupole- collective isovector valence-shell excitation — the states with so-called mixed proton-neutron symmetry (MSSs), in the nucleus 212Po. The states of interest were populated and studied by an α-transfer reaction. The experiment provides indication for existence of one-phonon MSS in the nucleus 212Po which is the first experimentally identified MSS in the region around double magic nucleus 208Pb

Low-lying isovector 2+ valence-shell excitations of 212^{212}Po

International audienceWe present the results from an experiment dedicated to search for quadrupole-collective isovector valence-shellexcitations, states with so-called mixed proton-neutron symmetry (MSS), of 212Po. This nucleus was studiedin an α-transfer reaction. The lifetimes of two short-lived excited states, candidates for the one-phonon MSS,were determined by utilizing the Doppler shift attenuation method. The experimental results are in qualitativeagreement with a simple single-j shell model calculation, which, together with the observed lack of quadrupolecollectivity, indicates that the isovector nature of low-lying states is a property of the leading single-particlevalence shell configuration

Microscopic structure of the one-phonon 2(+) states of Po-208

The lifetimes of the 2(1)(+) and 4(1)(+) states of Po-208 were measured in the a-transfer reaction Pb-204(C-12, Be-8) Po-208 by gamma-ray spectroscopy utilizing the recoil distance Doppler shift method. The newly extracted transition strengths alongside ones of the decay of the 2(2)(+) state were compared to the results of large-scale shell-model calculations using an effective interaction derived from the realistic CD-Bonn nucleon-nucleon potential. The comparison indicates the importance of the quadrupole isovector excitations in the valence shell for a fine tuning of the two-body matrix elements of the shell-model interaction

Lifetime measurements in the even-even isotopes

Background: The heaviest doubly-magic nucleus, , and the neighboring nuclei offer unique opportunities to investigate the properties of nuclear interaction. For instance, the structure of light-Sn nuclei has been shown to be affected by the delicate balance between nuclear-interaction components, such as pairing and quadrupole correlations. From Cd to Te, many common features and phenomena have been observed experimentally along the isotopic chains, leading to theoretical studies devoted to a more general and comprehensive study of the region. In this context, having only two proton holes in the shell, the Cd isotopes are expected to present properties similar to those found in the Sn isotopic chain. Purpose: The aim of this work was to measure lifetimes of excited states in neutron-deficient nuclei in the vicinity of . Results: Lifetimes of low-lying states were measured in the even-mass isotopes. In particular, multiple states with excitation energy up to MeV, belonging to various bands, were populated in via inelastic scattering. The transition strengths corresponding to the measured lifetimes were compared with those resulting from state-of-the-art beyond-mean-field calculations using the symmetry-conserving configuration-mixing approach. Methods: The neutron-deficient nuclei in the region were populated using a multinucleon transfer reaction with a beam and a target. The beamlike products were identified by the VAMOS spectrometer, while the rays were detected using the AGATA array. Lifetimes of excited states were determined using the recoil distance Doppler-shift method, employing the Cologne differential plunger. Conclusions: Despite the similarities in the electromagnetic properties of the low-lying states, there is a fundamental structural difference between the ground-state bands in the and isotopes. The comparison between experimental and theoretical results revealed a rotational character of the Cd nuclei, which have prolate-deformed ground states with . At this deformation becomes a closed-shell configuration, which is favored with respect to the spherical one

Lifetime measurements using a plunger device and the EUCLIDES Si array at the GALILEO \u3b3-ray spectrometer

The GALILEO \u3b3-ray spectrometer, installed at the Laboratori Nazionali di Legnaro (LNL), benefits from intense stable beams provided by the Tandem-ALPI-PIAVE accelerator complex and from radioactive beams to be delivered in the near future by the SPES facility. The spectrometer is complemented with a variety of ancillary devices to allow for nuclear structure and reaction studies. The 4\u3c0 Si-ball array EUCLIDES coupled to the GALILEO \u3b3-ray spectrometer represents one of the commonly used setup for experiments aiming at spectroscopic studies. High-efficiency detection of light-charged particles in a fusion\u2013evaporation reaction guarantees good discrimination of different reaction channels and provides essential information for the kinematic reconstruction. In this paper we discuss a configuration of the EUCLIDES array developed for the lifetime measurements of nuclear excited states populated in a fusion\u2013evaporation reaction. In such a configuration a part of the EUCLIDES detectors is disassembled allowing for the installation of a plunger device in the reaction chamber. The reduced configuration of EUCLIDES provides high detection efficiency necessary for reliable light charged-particle discrimination. We report on the commissioning experiment focused on the 58Ni(58Ni,3p)113I reaction. The lifetimes of 11/2 12 and 15/2 12 states were measured by applying the Recoil Distance Doppler Shift method to be equal to 206(20) ps and 7.9(12) ps correspondingly and were in good agreement with the values cited in the literature. Thus, the combination of the GALILEO and EUCLIDES arrays, and the plunger device has resulted in a powerful experimental setup to determine lifetimes of excited states in neutron-deficient nuclei in the picosecond range