Aikaterini Zyriliou

Even-even Yb and W isotopes around the N=104 mid-shell region are known to present deformation. The ground-band states of these nuclei are well described by the SU(3) symmetry, indicating a rigid-rotor character. Excited states of even-even isotopes in the region, namely 176Yb and 182W, were populated through Coulomb excitation and fusion-evaporation reactions, in an experiment performed at IFIN-HH in Măgurele, Romania. The gamma-spectroscopy of these nuclei will be presented in this contribution. Additionally, gamma spectroscopy results for the even-odd 177Yb nucleus, populated by the 1n-transfer reaction mechanism, will be presented. Contradictory to the collective description of the ground-band excitations in 176Yb and 182W isotopes, the excited states of this nucleus can be described by single-particle excitations. The gamma-spectroscopy analysis of this data contributes to the evaluation of the available data in this mass region, while ongoing work is expected to provide further insights for the nuclear structure of these rare-earth isotopes.

The isotopes of Tellurium are located near the stability line on the isotopic chart, making them important for study in the context of nuclear theory and in terms of applications. In this work, we present a study of the radioactive decay chains of Tellurium isotopes with mass numbers 117 and 115, aiming to investigate their ground-state half-lives as determined from an experiment conducted at the 9 MV Tandem accelerator at IFIN-HH in Romania. Key parts of this presentation are a novel approach used to extract the experimental half-life values, as well as its application to the experimental data obtained for the two Tellurium decay chains. A comparison of the results for the half-lives obtained with and without the application of this approach will also be presented to demonstrate its capabilities. The approach does not rely on any input from the literature, and it allows for a significant reduction in the uncertainties associated with the extracted half-life values, thus enhancing the reliability and precision of the results.

This work focuses on the lifetime measurement and spectroscopic properties of 182W. The mass region around this nucleus is of significant interest due to its unexplored nature and the presence of intriguing structural phenomena, including deformation, shape changes, and shape coexistence. Experimental measurements were conducted in the National Laboratory IFIN-HH in Romania, focused on the spectroscopic study of 182W isotope using the Differential Decay Curve Method (DDCM), a similar approach for the Recoil Distance Doppler Shift (RDDS) method. This experiment provided valuable data on the energy levels, lifetimes, and decay properties of the excited states in the 182W and neighboring nuclei. The measurements were performed using the ROSPHERE detector array, loaded with HPGe and particle identification detectors, and a plunger device. As a result, the lifetime for the 61+ in 182W obtained for the first time via the fusion evaporation reaction 181Ta(11B, 10Be)182W and the DDCM at 47 MeV, and was found to agree well with earlier measurements.

In the present work, a dedicated experimental study of the lifetimes of in Te and Sb isotopes was undertaken at the 9 MV Tandem accelerator at the IFIN-HH. Beams of 11B at 35 MeV impinged on a natAg target to populate the nuclei of interest and study their decay using the activation method. The emitted gamma rays and charged particles were detected by the ROSPHERE and SORCERER arrays. Lifetimes of the decaying isomeric and ground states in 117Te and 115,117Sb were measured. The present results update existing literature data from half a century ago employing a new reaction mechanism to populate the states of interest along with a more advanced array of detectors

The neutron–deficient region around the Z=50 major shell closure provides fertile grounds for nuclear structure studies, as single–particle degrees of freedom compete with collective phenomena to form several of the observed spectroscopic properties. This work reports on the progress and the preliminary results of a recent experiment performed at IFIN–HH, in Magurele, Romania, focused around the measurement of lifetimes of excited states in neutron–deficient Te isotopes, by means of the Fast Electronic Scintillation Timing (FEST, or fast–timing) technique. A 11B beam of Elab = 35 MeV impinging on a 5 mg/cm2 natAg target was used to populate excited states in 115−120Te. The γ rays de-exciting these levels were detected by the ROSPHERE array, in its mixed 15 HPGe + 10 LaBr3(Ce) detector configuration. Additionally, the SORCERER particle detector array was coupled to ROSPHERE, enabling the study of p-γ and p-γ-γ coincident events. The combination of experimental findings and theoretical predictions from several models, including the newly developed proxy-SU(3), is anticipated to offer valuable insights into the dynamic shape evolution of the investigated isotopes.

This work features preliminary results from a recent experimental campaign at IFIN-HH, Romania, aimed at measuring lifetimes of excited states in the neutron-rich 180Hf, by means of the RDDS technique. The 181Ta(11B,12C)180Hf proton pick-up reaction was used to populate excited states in the 180Hf nucleus. The ROSPHERE array loaded with 25 HPGe detectors was employed for the detection of the γ transitions depopulating the levels of interest. The array was coupled to the SORCERER particle detector and a plunger device enabling the study of p-γ and p-γ-γ coinciding events. Six different plunger foil distances were chosen, allowing for the construction of the decay curves of the observed γ transitions of interest, from which the corresponding level lifetimes can subsequently be deduced.

The medium-to-heavy mass ytterbium isotopes (70Yb) in the rare-earth mass region are known to be well-deformed nuclei, which can be populated to very high spin, and are predicted to exhibit interesting phenomena, such as shape coexistence. The lack of any experimental information on the structure of the neutron-rich 180Yb isotope and the lifetime of the 21+ state of 178Yb have greatly motivated this study, which can offer useful information for the collective behavior of neutrons and protons in neutron-rich Yb isotopes. A measurement was performed to investigate the population of excited states and a first measurement of the unknown 21+ lifetime of 178Yb by means of a two neutron-transfer reaction 176Yb(18O,16O)178Yb at energies 68-74 MeV using the ROSPHERE array at IFIN-HH, Romania.