Simple Nuclear Structure inCd111–129from Atomic Isomer Shifts

Abstract

Isomer shifts have been determined in [111][112][113][114][115][116][117][118][119][120][121][122][123][124][125][126][127][128][129] Cd by high-resolution laser spectroscopy at CERN-ISOLDE. The corresponding mean square charge-radii changes, from the 1=2 þ and the 3=2 þ ground states to the 11=2 − isomers, have been found to follow a distinct parabolic dependence as a function of the atomic mass number. Since the isomers have been previously associated with simplicity due to the linear mass dependence of their quadrupole moments, the regularity of the isomer shifts suggests a higher order of symmetry affecting the ground states in addition. A comprehensive description assuming nuclear deformation is found to accurately reproduce the radii differences in conjunction with the known quadrupole moments. This intuitive interpretation is supported by covariant density functional theory. DOI: 10.1103/PhysRevLett.116.032501 Complexity is known to dominate the nuclear state, hence, sustaining the need for theoretical input to nearly every experimental work in order to disentangle the nuclear problem down to a set of basic concepts, e.g., shell structure, pairing, "magic" numbers, deformation, etc. However, in near-closed-shell nuclei, simple structures may occur as a result of the spherical symmetry breaking up. The cadmium isotopic chain studied here appears to provide one such instance of simplicity.Already [4,5] or states in the same nucleus [6]. Thus far, radial changes of such magnitude appear to be uncommon, the other prominent examples being the halo structures in light nuclei [7][8][9][10][11] and the onset of deformation at N ¼ 60 [12][13][14][15][16]. Cadmium and mercury are analogues in terms of their charge distributions since both incorporate an open shell with two protons less than a magic number, respectively, Z ¼ 50 and Z ¼ 82. Despite the similarities, the cadmium case presented here shows no abrupt changes of the nuclear size. Instead, one observes a small-to-moderate effect on the radii characterized by regularity which may be attributed to the unique-parity h 11=2 orbital.In this Letter, we report on the simplicity of high-precision isomer shifts derived from collinear laser spectroscopy on the neutron-rich cadmium isotopes towards the N ¼ 82 shell closure. A comprehensive model resting on some of the basic concepts in nuclear physics suggests an apparent link between the 11=2 − radii and quadrupole moments. The credibility of such an interpretation is examined quantitatively within a relativistic mean field calculation.The work was carried out with the collinear laser spectroscopy setup at the CERN-ISOLDE radioactivebeam facility. Of interest were the odd neutron-rich

Precision mass measurements of Cd125–127 isotopes and isomers approaching the N=82 closed shell

“…Systematics here do not justify a tentative spin assignment, and therefore the spins must be measured directly. Yordanov et al recently performed isomeric frequency shift measurements in a collinear laser spectroscopy experiment [3,49]. While an energy difference of ∼ 250 keV would produce a frequency difference of ±1.3 MHz [50], that is approximately half the error stated in their publication [49] so laser spectroscopy alone cannot illuminate the spin assignments either.…”

Collinear laser spectroscopy at ISOLDE: new methods and highlights

“…This implies a rather large effective neutron charge of q e 2.5 n eff, = . Later it was shown that these assumptions can indeed be used to explain also the isomer shifts between the respective ground state and the isomer, which were found to follow a distinct parabolic dependence as a function of the atomic mass number [72]. Even though the nuclear shape is very close to spherical all along the isotopic chain and never exceeds a deformation parameter of 0.07, this unique regularity in the isomeric shift can be understood as a manifestation of nuclear deformation.…”

Ground state properties and potential energy surfaces of 270Hs from multidimensionally-constrained relativistic mean field model

“…As reviewed in Ref. [78], this empirical functional has been very successful in describing nuclear ground state properties, e.g., the Coulomb displacement energies between mirror nuclei [79], nuclear binding energies [80][81][82] and quadrupole moments [83][84][85] and phase transitions in the nuclear shape [86], and low-energy excited states including nuclear chiral rotations [87] and magnetic and antimagnetic rotations [88][89][90][91][92]. PC-PK1 has also been used to study properties of SHN [93][94][95].…”