0000000000230907
AUTHOR
Roger Silverans
Nuclear moments of strongly deformed strontium isotopes
Nuclear spins, moments and mean square charge radii of78–100Sr have been obtained by fast ion-beam collinear laserspectroscopy. The experiments performed at ISOLDE have been extended to include99Sr, measured by a non-optical detection scheme with a two-step optical pumping sequence. The results for the strongly deformed isotopes are discussed in the frame of the particle-plus-deformed core model.
Spin, moments, and mean square nuclear charge radius ofSr77
The neutron deficient $^{77}\mathrm{Sr}$ nucleus was studied by fast ion beam collinear laser spectroscopy with a detection scheme based on optical pumping, state selective neutralization, and atom counting. From the measured hyperfine splitting and isotope shift of the Sr II transition 5s $^{2}$${\mathit{S}}_{1/2}$\ensuremath{\rightarrow}5p $^{2}$${\mathit{P}}_{3/2}$ the nuclear spin I=5/2, the nuclear moments \ensuremath{\mu}=-0.348(4)${\mathrm{\ensuremath{\mu}}}_{\mathit{N}}$, ${\mathit{Q}}_{\mathit{s}}$=1.40(11) b, and the change in mean square charge radius \ensuremath{\delta}〈${\mathit{r}}^{2}$${\mathrm{〉}}^{88,77}$=0.248(12) ${\mathrm{fm}}^{2}$ were deduced. These ground-state proper…
On the odd-even staggering of mean-square charge radii in the light krypton and strontium region
Recently isotope shifts of $^{72,74-96}$Kr and $^{77-100}$Sr have been measured at the ISOLDE/ CERN mass separator facility by collinear laser spectroscopy. The deduced changes in mean square charge radii reveal sharp transitions in nuclear shape from spherical near the magic neutron number N=50 towards strongly deformed for both the neutron deficient and neutron rich isotopes far from stability. The mean square charge radii of the neutron deficient isotopes exhibit a sign change of the odd-even staggering (OES), i.e. below the neutron number N=46 the radius is systematically larger for the odd-N nuclei than for their even-N neighbours. This is in contrast to the situation of normal OES whi…
Systematics of nuclear ground state properties inSr78–100by laser spectroscopy
Hyperfine structures and isotope shifts of strontium isotopes with A=78 to A=98 and A=100 were measured by collinear fast beam laser spectroscopy. Nuclear spins, moments and changes in mean square charge radii are extracted from the data. The spins and moments of most of the odd isotopes are explained in the framework of the single particle model. The changes in mean square charge radii are compared with predictions of the droplet model and of Hartree-Fock-plus-BCS calculations. For the isotopes in the transitional regions below and above the N=50 shell closure, the inclusion of quadrupole zero point motion in the Droplet model describes part of the observed shell effect. An additional chan…
The electronic field shift factor of the 4s2S1/2?4p2PJ transitions in CaII
The isotope shifts (IS) of the resonance lines 4s2S1/2−4p2PJin CaII (seven isotopes) have been measured by fast ion beam collinear laser spectroscopy (FIBCLS) with non-optical detection of the resonant laser-ion interaction. The electronic field shift factorF was derived from the experimental IS via a King plot procedure using the mean square nuclear charge radii from muon spectroscopy andelectron scattering. TheJ-independent resultF=−283(6) Mhz/fm2 was obtained. TheF-value resulting from extensive many body perturbation theory (MBPT) calculations, recently performed by Martensson-Pendrill et al., is in excellent agreement with the experimental value, confirming the reliability of the MBPT …
Nuclear ground state spins of short-lived strontium isotopes
Nuclear ground state spins of the odd-mass strontium isotopes between A=79 and 97 were determined by measurements of the hyperfine structure in the ionic transition 5s2S1/2−5p2P3/2. The spins of93Sr and97Sr are revised to I=5/2 and I=1/2, respectively, while assignments for the remaining isotopes are confirmed.
Laser-spectroscopy measurements of 72–96Kr spins, moments and charge radii
Abstract The spins, moments and radii of krypton isotopes have been investigated by collinear fast-beam laser spectroscopy in combination with ultra-sensitive collisional ionization detection. The sequence of isotopes under study ranges from the neutron-deficient N = Z = 36 isotope 72 Kr to the neutron-rich 96 Kr ( N = 60). The mean-square charge radii in the neighbourhood of the N = 50 neutron-shell closure exhibit a pronounced shell effect which has recently been explained in the framework of relativistic mean-field theory. The results for the neutron-deficient nuclei are related to the shape coexistence of strongly prolate and near-spherical states which is known from nuclear spectroscop…
Moments and Radii of 78–100Sr
The chain of Sr isotopes ranges from the neutron-shell closure at N = 50 into both the N = 38 and N = 60 deformation regions which represent the main topic of this workshop. For a detailed understanding of the nature of these nuclei, laser spectroscopy can provide the ground state spins and moments, as well as the the changes in the mean square charge radii as a function of the neutron number N. Recent experiments at Karlsruhe [1] and at Daresbury [2] essentially cover the neutron-deficient and stable Sr isotopes between N = 40 and N = 50. In order to complement these results, and to extend the measurements into the region of neutron-rich isotopes, we have performed an experiment at the ISO…
Very high sensitivity in collinear laser spectroscopy: resonance detection by particle counting techniques
Abstract Fast-beam collinear laser spectroscopy with resonance detection by counting of fluorescence photons provides a versatile tool for precise determinations of nuclear ground-state properties. The intrinsic high sensitivity of this method can be further increased by almost three orders of magnitude if measuring schemes based on ion or atom counting are introduced. The optical pumping from one atomic state to another at an appreciably different excitation energy is detected via state-selective collisional charge exchange processes and charge-state separated atom or ion counting. Applications of these techniques on alkaline earth, noble gas, mercury and thallium beams is examined.
Decay pathways of stored metal-cluster anions after collisional activation
Size-selected gold clusters, Open image in new window (n ≤ 21), and tungsten clusters, Open image in new window , and Open image in new window (n = 4 – 8 and 12), stored in a Penning trap have been collisionally activated. Neutral monomer and dimer evaporation are observed in the case of gold. While no fragment products have been observed for tungsten clusters, there is evidence of electron emission from the anions.
Nuclear ground state properties of 99Sr by collinear laser spectroscopy with non-optical detection
Abstract Collinear fast-beam laser spectroscopy, with improved sensitivity for ions with hyperfine split transitions, is performed to measure the hyperfine structure and the isotope shift of the well deformed short-lived 99Sr. The new method consists in ground state depopulation by a two-step optical pumping sequence prior to state selective neutralization and fast-atom counting. A definitive nuclear spin value I = 3 2 , the change in mean square charge radius δ〈r2〉98,99 and the nuclear moments are derived. These results are compared to nuclear spectroscopy information and are interpreted in the frame of the particle plus deformed core model.
Hyperfine structure constants of the CaII states 4s 2 S 1/2 and 4p 2 P 1/2, 3/2 and the nuclear quadrupole moment of43Ca
The hyperfine structure splittings of the 4s 2 S 1/2 → 4p 2 P 1/2, 3/2 transitions in43CaII have been measured by fast ion beam collinear laser spectroscopy. The resonant laser interaction was observed using non-optical detection based on optical ground state depopulation pumping, state selective neutralization and charge state separated particle counting. The extracted magnetic dipole hyperfine structure constants for43CaA(2 S 1/2)=−805(2) MHz,A(2 P 1/2)=−145.5(1.0) MHz andA(2 P 3/2)=−31.9(0.2) MHz are in excellent agreement with relativistic many body perturbation theory predictions available for this alkali-like ion. The combined results are used to evaluate the semi-empirical analysis m…