Decay spectroscopy of the odd-proton nuclei
249
Md and
251
Md has been performed. High-
K
isomeric states were identified for the first time in these two nuclei through the measurement of their ...electromagnetic decay. An isomeric state with a half-life of 2.8(5) ms and an excitation energy
≥
910
keV was found in
249
Md. In
251
Md, an isomeric state with a half-life of 1.4(3) s and an excitation energy
≥
844
keV was found. Similarly to the neighbouring
255
Lr, these two isomeric states are interpreted as 3 quasi-particle high-
K
states and compared to new theoretical calculations. Excited nuclear configurations were calculated within two scenarios: via blocking nuclear states located in proximity to the Fermi surface or/and using the quasiparticle Bardeen–Cooper–Schrieffer method. Relevant states were selected on the basis of the microscopic-macroscopic model with a deformed Woods–Saxon potential. The most probable candidates for the configurations of
K
-isomeric states in Md nuclei are proposed.
VADER: A novel decay station for actinide spectroscopy Raggio, A.; Pohjalainen, I.; Rey-Herme, E. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
July 2023, 2023-07-00, Letnik:
540
Journal Article
Recenzirano
Odprti dostop
A research programme focused on the study of the nuclear structure of actinide isotopes has recently been implemented at the IGISOL facility, University of Jyväskylä. Within this scope, a new decay ...station named VADER (Versatile Actinides DEcay spectRoscopy setup) has been developed and commissioned. The system consists of a compact array of silicon detectors, a liquid-nitrogen-cooled silicon lithium (Si(Li)) detector and three broad energy germanium detectors (BEGe), placed around a thin implantation carbon foil. The combined use of different detectors allows the measurement of α particles, conversion electrons and de-excitation γ rays in coincidence, enabling a full reconstruction of nuclear decay schemes. The measurement of basic nuclear decay observables provides a picture of the nuclear shell evolution in neutron-deficient actinides, and highlights the possible emergence of reflection-asymmetric shapes in the region.
Decay spectroscopy of the odd-proton nuclei $^{249}$Md and $^{251}$Md has
been performed. High-$K$ isomeric states were identified for the first time in
these two nuclei through the measurement of ...their electromagnetic decay. An
isomeric state with a half-life of $2.8(5)$ ms and an excitation energy $\geq
910$ keV was found in $^{249}$Md. In $^{251}$Md, an isomeric state with a
half-life of $1.4(3)$ s and an excitation energy $\geq 844$ keV was found.
Similarly to the neighbouring $^{255}$Lr, these two isomeric states are
interpreted as 3 quasi-particle high-$K$ states and compared to new theoretical
calculations. Excited nuclear configurations were calculated within two
scenarios: via blocking nuclear states located in proximity to the Fermi
surface or/and using the quasiparticle Bardeen-Cooper-Schrieffer method.
Relevant states were selected on the basis of the microscopic-macroscopic model
with a deformed Woods-Saxon potential. The most probable candidates for the
configurations of $K$-isomeric states in Md nuclei are proposed.
The odd-\(Z\) \(^{251}\)Md nucleus was studied using combined \(\gamma\)-ray and conversion-electron in-beam spectroscopy. Besides the previously observed rotational band based on the \(5211/2^-\) ...configuration, another rotational structure has been identified using \(\gamma\)-\(\gamma\) coincidences. The use of electron spectroscopy allowed the rotational bands to be observed over a larger rotational frequency range. Using the transition intensities that depend on the gyromagnetic factor, a \(5147/2^-\) single-particle configuration has been inferred for this band, i.e., the ground-state band. A physical background that dominates the electron spectrum with an intensity of \(\simeq\) 60% was well reproduced by simulating a set of unresolved excited bands. Moreover, a detailed analysis of the intensity profile as a function of the angular momentum provided a method for deriving the orbital gyromagnetic factor, namely \(g_K = 0.69^{+0.19}_{-0.16}\) for the ground-state band. The odd-\(Z\) \(^{249}\)Md was studied using \(\gamma\)-ray in-beam spectroscopy. Evidence for octupole correlations resulting from the mixing of the \(\Delta l = \Delta j = 3\) \(5213/2^-\) and \(6337/2^+\) Nilsson orbitals were found in both \(^{249,251}\)Md. A surprising similarity of the \(^{251}\)Md ground-state band transition energies with those of the excited band of \(^{255}\)Lr has been discussed in terms of identical bands. Skyrme-Hartree-Fock-Bogoliubov calculations were performed to investigate the origin of the similarities between these bands.
Decay spectroscopy of the odd-proton nuclei \(^{249}\)Md and \(^{251}\)Md has been performed. High-\(K\) isomeric states were identified for the first time in these two nuclei through the measurement ...of their electromagnetic decay. An isomeric state with a half-life of \(2.8(5)\) ms and an excitation energy \(\geq 910\) keV was found in \(^{249}\)Md. In \(^{251}\)Md, an isomeric state with a half-life of \(1.4(3)\) s and an excitation energy \(\geq 844\) keV was found. Similarly to the neighbouring \(^{255}\)Lr, these two isomeric states are interpreted as 3 quasi-particle high-\(K\) states and compared to new theoretical calculations. Excited nuclear configurations were calculated within two scenarios: via blocking nuclear states located in proximity to the Fermi surface or/and using the quasiparticle Bardeen-Cooper-Schrieffer method. Relevant states were selected on the basis of the microscopic-macroscopic model with a deformed Woods-Saxon potential. The most probable candidates for the configurations of \(K\)-isomeric states in Md nuclei are proposed.
The radiation detection resonance ionization spectroscopy (RADRIS) technique enables laser spectroscopic investigations of the heaviest elements which are produced in atom-at-a-time quantities from ...fusion-evaporation reactions. To achieve a high efficiency, laser spectroscopy is performed in a buffer-gas environment used to thermalize and stop the high-energy evaporation residues behind the velocity filter SHIP. The required cyclic measurement procedure in combination with the applied filament collection for neutralization as well as confinement of the stopped ions and subsequent pulse-heat desorption constrains the applicability of the technique. Here, some of these limitations and also opportunities that arise from this unique measurement setup will be evaluated.
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