Changes in nuclear structure along the Mn isotopic chain studied via charge radii

Abstract

The hyperfine spectra of 51,53−64 Mn were measured in two experimental runs using collinear laser spectroscopy at ISOLDE, CERN. Laser spectroscopy was performed on the atomic 3d 5 4s 2 6 S 5/2 → 3d 5 4s4p 6 P 3/2 and ionic 3d 5 4s 5 S2 → 3d 5 4p 5 P3 transitions, yielding two sets of isotope shifts. The mass and field shift factors for both transitions have been calculated in the multiconfiguration Dirac-Fock framework and were combined with a King plot analysis in order to obtain a consistent set of mean-square charge radii which, together with earlier work on neutrondeficient Mn, allow the study of nuclear structure changes from N = 25 across N = 28 up to N = 39. A clear development of deformation is observed towards N = 40, confirming the conclusions of the nuclear moments studies. From a Monte Carlo Shell Model study of the shape in the Mn isotopic chain, it is suggested that the observed development of deformation is not only due to an increase in static prolate deformation but also due to shape fluctuations and triaxiality. The changes in mean-square charge radii are well reproduced using the Duflo-Zuker formula except in the case of large deformation.

Collinear laser spectroscopy at ISOLDE: new methods and highlights

“…A comparison of the magnetic and quadrupole moments with large scale shell model calculations in different model spaces shows that proton excitation across Z=28 as well as neutron excitation across N=40 and N=50 (into the g 9 2 and d 5 2 orbits) are needed to reproduce the observed values from N=36 onwards [58,61]. The slope in the charge radii of the Mn isotopes clearly increases from N=36 onwards, confirming the increase in deformation that was observed also in the quadrupole moments [60]. This is best seen in figure 5(b) where the charge radii of all isotopic chains are plotted relative to the value at N=30.…”

“…A decrease in the radii is seen towards N=28 and a steep increase is observed when crossing the N=28 shell gap. No signature for a shell closure at N=32 is seen for Ca and K. Taken from [48,54,60,64,68]. (b) Radii relative to the N=30 value for each isotopic chain: the radii follow a remarkable similar increase beyond N=28, highlighting the sudden onset of deformation in the Mn radii beyond N=36.…”

Multiconfiguration calculations of electronic isotope shift factors in Al i

“…The second approach was applied to heavier elements such as polonium [13], where a good consistency with a King plot analysis was obtained. A similar consistency check was also performed on two transitions in manganese [14], where excellent agreement for the mass-shift factors computed with RIS3 was observed.…”

Emergence of simple patterns in many-body systems: from macroscopic objects to the atomic nucleus

“…Recent developments in both experimental and theoretical tools have provided a deeper insight in our understand-ing of nuclear properties at extreme proton-to-neutron ratios. Particular interest has been focused on the evolution of nuclear properties towards the suggested neutron-rich doubly-magic nuclei: 52,54 Ca (Z = 20, N = 32,34) [101,114,115,121], 78 Ni (Z = 28, N = 50) [123,124,156,157], and 132 Sn (Z = 50, N = 82) [127,128]. These regions of the nuclear chart are being studied by several experimental techniques proving tests of theoretical descriptions at limits of the nuclear existence.…”