[en] Within the framework of our studies of proton rich nuclei around the N 126 and N = 152 neutron shells we have performed a series of α-γ-coincidence studies. The nuclei of interest were separated in-flight by the velocity filter SHIP and implanted into a position sensitive 16-strip PIPS-detector where their arrival and subsequent α-decays were registered. Associated γ-rays were detected by a Ge-Clover-detector. In the present work recent results concerning 216Th and α-decay chains of 251No and 257Db are given together with brief discussion

[en] During summer 2018 direct mass measurements of transfermium isotopes such as ${}^{251}$No (Z=102), ${}^{254}$Lr (Z=103) as well as the first superheavy element ${}^{257}$Rf (Z=104) have been successfully achieved, for the first time, with the SHIPTRAP mass spectrometer. Moreover, exploiting the enhanced resolving power of the Phase-Imaging Ion-Cyclotron-Resonance technique, it was also possible to directly resolve, for the first time, the low-lying isomeric states ${}^{251m}$No and ${}^{254m,255m}$Lr and the K${}^{\mathrm{\pi <!--\; ??\; -->}}$=8${}^{-<!--\; ???\; -->}$ isomer ${}^{254m}$No with a Penning-trap system. These results will shed light on the nuclear shell effects that determine regions of enhanced shell stabilization as for instance nearby the deformed neutron shell at N=152 and are closely linked to the existence of such heavy nuclei as bound systems. Furthermore, such investigations will enable a better understanding of the nature of the underlying strong interaction at the upper limit of the nuclear chart and will help to constrain predictions for the next spherical shell closures, expected by different models around Z=114, N=184, the so-called island of stability. Such challenging experiments face the problem of very low production rates, down to few ions per hour(s) which demand a very efficient ion preparation and manipulation, coupled with a high-detection sensitivity and resolving power. In this talk an overview of the latest optimization and enhanced performances of the SHIPTRAP setup will be presented together with the recent experimental results.

[en] Radioactive decay from the ground state or isomeric states has been investigated for a series of nuclei in the region of Z = 100-106 by means of α-γ-or evaporation residue-(γ, conversion electron)-measurements in prompt and delayed coincidence. Systematic trends in single-particle level energies in N = 145-151 odd-even isotones could be extended up to Z = 104, while an energy systematics of lowlying Nilsson levels in odd-mass einsteinium isotopes was established. Information on nuclear levels at E* > 500 keV was obtained from the decay study of isomeric states in ^251-255No

[en] Nuclear spectroscopic information for known nuclides of mass number 251 with Z = 96 to 102 (Cm,Bk,Cf,Es, Fm,Md,No) and N = 155 to 149 have been evaluated and presented together with adopted energies and Jπ of levels in these nuclei. No excited state data are yet available for ²⁵¹Cm. This evaluation supersedes previous full evaluation of A = 251 by A. Artna-Cohen (1999Ar21) with literature cutoff date of Jul 1999. Inconsistencies and discrepancies are noted. The adopted values of level energies, level spins and parities are given, and γ-ray energies, γ-ray intensities, as well as other nuclear properties are presented. The references, Jπ arguments, and necessary comments are given. Theoretical studies are given as comments. New measurements have been reported in ²⁵¹No, ²⁵¹Md, ²⁵¹Cf and ²⁵¹Es. All adopted Q values are from 2003Au03. 2004Pa31 give calculated neutron separation energy by a macroscopic-microscopic approach

[en] The decay of the isotopes ²⁵⁵Rf, ²⁵¹No and ²⁴⁷Fm produced in the reactions ²⁰⁷Pb(⁵⁰Ti,2n)²⁵⁵Rf^α_→²⁵¹No^α_→²⁴⁷Fm, and ²⁰⁶Pb(⁴⁸Ca,3n)²⁵¹No^α_→²⁴⁷Fm was investigated by means of α-γ spectroscopy. Previously observed γ transitions in coincidence with α decays of ²⁵⁵Rf were confirmed, their energies and line intensities were measured more precisely, and their multipolarities were determined as E1. In ²⁵¹No a new isomeric state at E^*>1700 keV with a half-life of ∼2μs was identified. The decay of ²⁴⁷Fm was measured more precisely. A partial level scheme of the daughter nucleus ²⁴³Cf could be established. (orig.)

No abstract available

[en] The isotopic dependence of K-isomer states in heavy nuclei is treated. (author)

[en] The isotopes ²⁵¹No and ²⁵³No were produced in nuclear reactions ²⁰⁶Pb(⁴⁸Ca,3n)²⁵¹No and ²⁰⁷Pb(⁴⁸Ca,2n) ²⁵³No. Radioactive decay of these isotopes and their daughter products has been investigated by means of α- and α-γ- spectroscopy. An isomeric state ^251mNo, having a half-life of T_1/2=(0.93±0.06) s and decaying by emission of α particles of E_α=(8665±8) keV was identified. The measured decay data allowed for the construction of partial level schemes for ²⁵¹No, ^247,249Fm and ^243,245Cf and an extrapolation of energy systematics of single particle levels of N=145, 147 and 149 isotones with even Z towards higher atomic numbers up to Z=102. (orig.)

[en] The dynamical cluster-decay model (DCM) is used to calculate the fusion evaporation residue cross-sections σ_x_n for x=1-4 neutron emissions in the fusion reaction "2"0"6Pb+"4"8Ca → "2"5"4No* at various incident energies. Considering the multipole deformations up to hexadecapole deformations β_4_i and configurations with 'compact' orientation angles θ_c_i (θ_c=2"0 for "2"0"6Pb), the model is shown to give a good description of the measured individual light-particle decay channels, within one parameter fitting, the neck-length ΔR. Considering "2"0"4","2"0"6","2"0"7","2"0"8Pb-based reactions, the dependence of 2n-emission yields on the isotopic composition of compound nucleus (CN) is also studied within the DCM. Of the four Pb-isotopes considered, at a fixed excitation energy E*∼20 MeV, ΔR is largest for CN with mass number 256, followed by 255, 254 and smallest for 252, which means to suggest that neutrons emission occurs earliest for 256, then for 255, 254 and finally for 252, in complete agreement with experimental data where "2"5"6No* has the highest cross-section and "2"5"2No* the lowest with "2"5"5","2"5"4No* lying in between. This result arises due to the penetrability factor, and is related to double magic numbers of both target and projectile nuclei. (authors)

No abstract available