[paper] Interplay between nuclear shell evolution and shape deformation revealed by the magnetic moment of 75Cu

Interplay between nuclear shell evolution and shape deformation revealed by the magnetic moment of 75Cu

Y. Ishikawa et al.
Nature Physics (2019)
DOI: 10.1038/s41567-018-0410-7

Exotic nuclei are characterized by having a number of neutrons (or protons) in excess relative to stable nuclei. Their shell structure, which represents single-particle motion in a nucleus, may vary due to nuclear force and excess neutrons, in a phenomenon called shell evolution. This effect could be counterbalanced by collective modes causing deformations of the nuclear surface. Here, we study the interplay between shell evolution and shape deformation by focusing on the magnetic moment of an isomeric state of the neutron-rich nucleus 75Cu. We measure the magnetic moment using highly spin-controlled rare-isotope beams and achieve large spin alignment via a two-step reaction scheme that incorporates an angular-momentum-selecting nucleon removal. By combining our experiments with numerical simulations of many-fermion correlations, we find that the low-lying states in 75Cu are, to a large extent, of single-particle nature on top of a correlated 74Ni core. We elucidate the crucial role of shell evolution even in the presence of the collective mode, and within the same framework we consider whether and how the double magicity of the 78Ni nucleus is restored, which is also of keen interest from the perspective of nucleosynthesis in explosive stellar processes.

[paper] Isoscalar Spin Matrix Elements in s–d Shell Nuclei

Isoscalar Spin Matrix Elements in s–d Shell Nuclei

by Akito Arima and Wolfgang Bentz

doi: 10.7566/JPSCP.23.012011

The quenching of isovector spin matrix elements in s–d shell nuclei is well established experimentally as well as theoretically [1,2,3]. The isoscalar spin gyromagnetic ratios gsIS of nuclei with one nucleon or hole outside of LS closed shells are also quenched by the same mechanism. On the other hand, their isoscalar orbital gyromagnetic ratios gLIS are slightly enhanced by meson exchange currents [1,2]. Then we are interested very much in the following question: Are the isoscalar spin matrix elements generally quenched in s–d shell nuclei? We will try to answer this question in this paper.

Probing Sizes and Shapes of Nobelium Isotopes by Laser Spectroscopy

Until recently, ground-state nuclear moments of the heaviest nuclei could only be inferred from nuclear spectroscopy, where model assumptions are required. Laser spectroscopy in combination with modern atomic structure calculations is now able to probe these moments directly, in a comprehensive and nuclear-model-independent way. Here we report on unique access to the differential mean-square charge radii of 252,253,254No, and therefore to changes in nuclear size and shape. State-of-the-art nuclear density functional calculations describe well the changes in nuclear charge radii in the region of the heavy actinides, indicating an appreciable central depression in the deformed proton density distribution in 252,254No isotopes. Finally, the hyperfine splitting of 253No was evaluated, enabling a complementary measure of its (quadrupole) deformation, as well as an insight into the neutron single-particle wave function via the nuclear spin and magnetic moment.

 

Figure 3

Read the full article on Phys. Rev. Lett

A little bit of history

I am in the process of upgrading the database and I ran onto this article by de Shalit from 1951. A little piece of history, with ideas still holding.

Thanks to ETH for digitizing the entire collection of Helvetica Acta.

Here is the (open-access) article: [-link]

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Our provider has kindly upgraded security on the website by installing a SSl certificate.

https://magneticmoments.info welcome!

-tjm

[paper] Perturbed angular distributions with LaBr3 detectors: The $g$ factor of the first 10$^+$ state in $^{110}$Cd reexamined

Perturbed angular distributions with LaBr3  detectors: The g factor of the first 10+  state in 110Cd reexamined

T.J. Gray et al.

doi: 10.1103/PhysRevC.96.054332

The time differential perturbed angular distribution technique with LaBr3 detectors has been applied to the Iπ=11/2 isomeric state (Ex = 846 keV, τ=107 ns) in 107Cd, which was populated and recoil-implanted into a gadolinium host following the 98Mo(12C, 3n)107Cd reaction. The static hyperfine field strength of Cd recoil implanted into gadolinium was thus measured, together with the fraction of nuclei implanted into field-free sites, under similar conditions as pertained for a previous implantation perturbed angular distribution
g-factor measurement on the Iπ=10+ state in 110Cd. The 110Cd g(10+) value was thereby reevaluated, bringing it into agreement with the value expected for a seniority-two νh11/2 configuration.

[paper] In-gas-cell laser spectroscopy of the magnetic dipole moment of the N≈126 isotope 199Pt

In-gas-cell laser spectroscopy of the magnetic dipole moment of the N≈126 isotope 199Pt

Y. Hirayama et al.
doi: 10.1103/PhysRevC.96.014307

The magnetic dipole moment and mean-square charge radius of 199gPt (Iπ= 5/2,t1/2=30.8 min) ground state and 199mPt (Eex=424 keV, Iπ= (13/2)+,t1/2=13.6 s) isomeric state are evaluated for the first time from investigations of the hyperfine splitting of the λ1=248.792 nm transition by in-gas-cell laser ionization spectroscopy. Ground and isomeric states of neutron-rich 199Pt nucleus were produced by a multinucleon transfer reaction at the KEK Isotope Separation System (KISS), designed for the study of nuclear spectroscopy in the vicinity of N=126. The measured magnetic dipole moments +0.75(8)μN and 0.57(5)μN are consistent with the systematics of those of nuclei with Iπ= 5/2 and Iπ= 13/2+, respectively.

Getting ready for HNPS2017

It’s been a while since my last blog post. I have been really busy with end of the semester and preparing for a couple of Conferences where our group are participating.

The first one is coming up this weekend, Friday and Saturday 9-10.06.2017. It is the 26th Annual Symposium of our Hellenic Nuclear Physics Society, our little body of nuke people who gather together, present their recent works and give lots of space to young researchers to immense in what is going on in our field.

This year we have prepared an impressive number of 7 posters and 1 oral talk spanning all aspects of our scientific activities. The NuSTRAP group are active in three main directions, namely nuclear structure, nuclear reactions and applications of radiation including instrumentation and environmental studies. Despite being mostly preliminary, our results are publicly available online. You can visit this page to view our recent posters and if you fancy, give us some feedback or publicize our work to the social media. I stress out the fact that the majority of the work has been carried out by undergrads who spend a lot of time and showed exceptional eagerness to advance science while getting educated.

We will be standing next to our posters this coming Friday and Saturday, here is a link to the official program of HNPS2017. This is the list of posters:

  1. doi: 10.6084/m9.figshare.5084128 (S. Kolovi et al.)
  2. doi: 10.6084/m9.figshare.5080099 (C. Andrikopoulos et al.)
  3. doi: 10.6084/m9.figshare.5072245 (E.-M. Lykiardopoulou et al.)
  4. doi: 10.6084/m9.figshare.5086039 (I. Sideris et al.)
  5. doi: 10.6084/m9.figshare.5057854 (V. Lagaki et al.)
  6. doi: 10.6084/m9.figshare.5071840 (G. Zagoraios et al.)
  7. doi: 10.6084/m9.figshare.5089747 (N. Togia et al.)

I will be tweeting using the hashtag #hnps2017, so if you are a fellow tweep, please stand by.

[paper] Spin and magnetic moment of 23Mg

Spin and magnetic moment of 23Mg

D. Yordanov et al.

doi: 10.1088/1361-6471/aa718b

A negative magnetic moment of 23Mg has been determined by high-resolution laser spectroscopy at CERN-ISOLDE. The absolute value is in agreement with previous measurements by nuclear magnetic resonance while the sign points at high-seniority configurations. The result is consistent with shell-model predictions for nuclei with valence nucleons in the sd shell.

[paper] Onset of deformation in neutron-deficient Bi isotopes studied by laser spectroscopy

Onset of deformation in neutron-deficient Bi isotopes studied by laser spectroscopy

A.E. Barzakh et al.

doi: 10.1103/PhysRevC.95.044324

In-source laser spectroscopy experiments for bismuth isotopes at the 306.77-nm atomic transition has been carried out at the Investigation of Radioactive Isotopes on Synchrocyclotron facility of Petersburg Nuclear Physics Institute. New data on isotope shifts and hyperfine structure for Bi ground states and isomers (189,190m1,190m2,191,192,192m,194,194m,198mBi) have been obtained. The changes in the mean-square charge radii δ⟨r2⟩ and magnetic-moment values have been deduced. For Bi nuclei a marked deviation from the isotopic trend of δ⟨r2⟩ in lead and thallium isotopic chains has been demonstrated at N<111. This has been interpreted as an indication of the onset of quadrupole deformation. Analysis of the magnetic moments for odd-odd Bi isotopes also points to the possible increase in deformation at N<111.

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