36 research outputs found
Collinear laser spectroscopy of atomic cadmium
Hyperfine structure and factors of the atomic 5s\,5p\,\; ^3\rm{P}_2
\rightarrow 5s\,6s\,\; ^3\rm{S}_1 transition are determined from collinear
laser spectroscopy data of Cd and Cd. Nuclear
magnetic moments and electric quadrupole moments are extracted using reference
dipole moments and calculated electric field gradients, respectively. The
hyperfine structure anomaly for isotopes with and nuclear
ground states and isomeric states is evaluated and a linear
relationship is observed for all nuclear states except . This
corresponds to the Moskowitz-Lombardi rule that was established in the mercury
region of the nuclear chart but in the case of cadmium the slope is
distinctively smaller than for mercury. In total four atomic and ionic levels
were analyzed and all of them exhibit a similar behaviour. The electric field
gradient for the atomic 5s\,5p\,\; ^3\mathrm{P}_2 level is derived from
multi-configuration Dirac-Hartree-Fock calculations in order to evaluate the
spectroscopic nuclear quadrupole moments. The results are consistent with those
obtained in an ionic transition and based on a similar calculation.Comment: 12 pages, 5 figure
Voltage scanning and technical upgrades at the Collinear Resonance Ionization Spectroscopy experiment
To optimize the performance of the Collinear Resonance Ionization
Spectroscopy (CRIS) experiment at CERN-ISOLDE, technical upgrades are
continuously introduced, aiming to enhance its sensitivity, precision,
stability, and efficiency. Recently, a voltage-scanning setup was developed and
commissioned at CRIS, which improved the scanning speed by a factor of three as
compared to the current laser-frequency scanning approach. This leads to faster
measurements of the hyperfine structure for systems with high yields (more than
a few thousand ions per second). Additionally, several beamline sections have
been redesigned and manufactured, including a new field-ionization unit, a
sharper electrostatic bend, and improved ion optics. The beamline upgrades are
expected to yield an improvement of at least a factor of 5 in the
signal-to-noise ratio by suppressing the non-resonant laser ions and providing
time-of-flight separation between the resonant ions and the collisional
background. Overall, the presented developments will further improve the
selectivity, sensitivity, and efficiency of the CRIS technique.Comment: 10 pages. Under review at NIM B as part of the proceedings of EMIS
2022 at RAON, South Kore
Electromagnetic Properties of Indium Isotopes Elucidate the Doubly Magic Character of <sup>100</sup>Sn
Understanding the nuclear properties in the vicinity of 100Sn â suggested to be the heaviest doubly magic nucleus with equal proton number Z and neutron number N â has been a long-standing challenge for experimental and theoretical nuclear physics. In particular, contradictory experimental evidence exists regarding the role of nuclear collectivity in this region of the nuclear chart. Here, we provide additional evidence for the doubly-magic character of 100Sn by measuring the ground-state electromagnetic moments and nuclear charge radii of indium (Z = 49) isotopes as N approaches 50 from above using precision laser spectroscopy. Our results span almost the complete range between the two major neutron closed shells at N = 50 and N = 82 and reveal parabolic trends as a function of the neutron number, with a clear reduction toward these two neutron closed-shells. A detailed comparison between our experimental and numerical results from two complementary nuclear many-body frameworks, density functional theory and ab initio methods, exposes deficiencies in nuclear models and establishes a benchmark for future theoretical developments.<br/
Regional mechanical and biochemical properties of the porcine cortical meninges
peer-reviewedThe meninges are pivotal in protecting the brain against traumatic brain injury (TBI), an ongoing issue in most mainstream sports. Improved understanding of TBI biomechanics and pathophysiology is desirable to improve preventative measures, such as protective helmets, and advance our TBI diagnostic/prognostic capabilities. This study mechanically characterised the porcine meninges by performing uniaxial tensile testing on the dura mater (DM) tissue adjacent to the frontal, parietal, temporal, and occipital lobes of the cerebellum and superior sagittal sinus region of the DM. Mechanical characterisation revealed a significantly higher elastic modulus for the superior sagittal sinus region when compared to other regions in the DM. The superior sagittal sinus and parietal regions of the DM also displayed local mechanical anisotropy. Further, fatigue was noted in the DM following ten preconditioning cycles, which could have important implications in the context of repetitive TBI. To further understand differences in regional mechanical properties, regional variations in protein content (collagen I, collagen III, fibronectin and elastin) were examined by immunoblot analysis. The superior sagittal sinus was found to have significantly higher collagen I, elastin, and fibronectin content. The frontal region was also identified to have significantly higher collagen I and fibronectin content while the temporal region had increased elastin and fibronectin content. Regional differences in the mechanical and biochemical properties along with regional tissue thickness differences within the DM reveal that the tissue is a non-homogeneous structure. In particular, the potentially influential role of the superior sagittal sinus in TBI biomechanics warrants further investigation
The aged niche disrupts muscle stem cell quiescence
SUMMARY The niche is a conserved regulator of stem cell quiescence and function. During aging, stem cell function declines. To what extent and by which means age-related changes within the niche contribute to this phenomenon are unknown. We demonstrate that the aged muscle stem cell niche, the muscle fiber, expresses FGF2 under homeostatic conditions, driving a subset of satellite cells to break quiescence and lose self-renewing capacity. We show that relatively dormant aged satellite cells robustly express Sprouty1 (spry1), an inhibitor of FGF signalling. Increasing FGF signalling in aged satellite cells under homeostatic conditions by removing spry1, results in the loss of quiescence, satellite cell depletion and diminished regenerative capacity. Conversely, reducing niche-derived FGF activity through inhibition of FGFR1 signalling or overexpression of spry1 in satellite cells prevents their depletion. These experiments identify an age-dependent change in the stem cell niche that directly influences stem cell quiescence and function
Nuclear charge radii of â¶ÂČâ»âžâ°Zn and their dependence on cross-shell proton excitations
Nuclear charge radii of â¶ÂČâ»âžâ°Zn have been determined using collinear laser spectroscopy of bunched ion beams at CERN-ISOLDE. The subtle variations of observed charge radii, both within one isotope and along the full range of neutron numbers, are found to be well described in terms of the proton
excitations across the Z = 28 shell gap, as predicted by large-scale shell model calculations. It comprehensively explains the changes in isomer-to-ground state mean square charge radii of â¶âčâ»â·âčZn, the inversion of the
odd-even staggering around N = 40 and the odd-even staggering systematics of the Zn charge radii. With two protons above Z = 28, the observed charge radii of the Zn isotopic chain show a cumulative effect of different aspects of nuclear structure including single particle structure, shell closure, correlations and deformations near the proposed doubly magic nuclei, â¶âžNi and â·âžNi
Collinear laser spectroscopy at ISOLDE:New methods and highlights.
Over three and a half decades of collinear laser spectroscopy and the COLLAPS setup have played a major role in the ISOLDE physics programme. Based on a general experimental principle and diverse approaches towards higher sensitivity, it has provided unique access to basic nuclear properties such as spins, magnetic moments and electric quadrupole moments as well as isotopic variations of nuclear mean square charge radii. While previous methods of outstanding sensitivity were restricted to selected chemical elements with special atomic properties or nuclear decay modes, recent developments have yielded a breakthrough in sensitivity for nuclides in wide mass ranges. These developments include the use of bunched beams from the radiofrequency quadrupole coolerâbuncher ISCOOL, which allows a suppression of background by several orders of magnitude. Very recently, the combination of collinear laser spectroscopy with the principle of laser resonance ionisation took shape in the new CRIS setup, providing a very selective and efficient detection of optical resonance. We outline the basic experimental developments and discuss important results on nuclei or chains of isotopes in different mass ranges
Quadrupole moments of <sup>29</sup>Mg and <sup>33</sup>Mg
The quadrupole moments of 29Mg and 33Mg have been constrained by collinear
laser spectroscopy at CERN-ISOLDE. The values are consistent with shell-model
predictions, thus supporting the current understanding of light nuclei
associated with the "island of inversion"
Cu charge radii reveal a weak sub-shell effect at N=40
Collinear laser spectroscopy on 58â75Cu isotopes was performed at the CERN-ISOLDE radioactive ion beam
facility. In this paper we report on the isotope shifts obtained from these measurements. State-of-the-art atomic
physics calculations have been undertaken in order to determine the changes in mean-square charge radii ÎŽr2A,A
from the observed isotope shifts. A local minimum is observed in these radii differences at N = 40, providing
evidence for a weak N = 40 sub-shell effect. However, comparison of ÎŽA,A
with a droplet model prediction
including static deformation deduced from the spectroscopic quadrupole moments, points to the persistence of
correlations at N = 40.status: publishe