First isomeric quadrupole moment measured in fragmentation reactions: The case ofFe61m(

Abstract

This paper demonstrates the feasibility of quadrupole moment measurements on isomeric levels populated in projectile fragmentation reactions. The neutron-rich 61 Fe(9/2 + ) [E * = 861 keV, T 1/2 = 239(5) ns] isomer was produced and spin aligned by the intermediate energy fragmentation of a 64 Ni beam and implanted in a Cd single crystal. Its spectroscopic quadrupole moment |Q s | = 41(6) e fm 2 agrees with mean-field based calculations using the finite-range Gogny force, suggesting a moderately deformed shape characterized by an intrinsic charge quadrupole moment Q 0 = −85 e fm 2 or Q 0 = +115 e fm 2 . The present measurement paves the way for future determinations of isomeric quadrupole moments in more exotic nuclei.

Projected shell model description for high-spin states in neutron-rich Fe isotopes

“…This may suggest a coexistence of prolate and oblate shapes at a similar energy depth. We note that in the neighboring odd-mass 61 Fe, a recent measurement of the quadrupole moment of the 861-keV, 9/2 + isomeric state [30] implied a deformation β 2 ≈ +0.24 or −0.21. The authors in Ref.…”

Low-energy level schemes of66,68Fe and inferred proton and neutron excitations acrossZ=28Liddick1, Abromeit2, Ayres3 et al. 2013Phys. Rev. C217126View full textAdd to dashboardCite

“…Excited states originating from neutron excitations from the pf shell into the neutron g 9/2 single-particle state across N = 40 are observed in all neutron-rich odd-A Fe isotopes starting at N = 33. Levels with tentative spin and parity assignments of 9/2 + have been identified in 59 26 Fe 33 [6] and 61 26 Fe 35 [7][8][9], and inferred in 63 26 Fe 37 [9], 65 26 Fe 39 [8][9][10], and 67 26 Fe 41 [8,11], though in 67 Fe alternative positive parity states cannot be exclusively ruled out [12]. The 9/2 + levels in the odd-A Fe isotopes decrease from 1517-keV in 59 Fe to approximately 400 keV in both 65,67 Fe [10].…”

βdecay of61Mn to levels in61Fe

“…The spectroscopic quadrupole moment was determined to be |Q s | = 41(6)efm 2 [27]. A perturbed angular distribution function analysis [27] concluded that the 207-keV transition has a M 1 multipolarity, while the 654-keV one has M 2. Prolate deformation was suggested for the isomeric state and possible excited states on top of it, analogous to experimental data for 57,59 Fe [28,29].…”

“…The half-life of the isomeric state was determined with a better precision: 239(5) ns [26]. The spectroscopic quadrupole moment was determined to be |Q s | = 41(6)efm 2 [27]. A perturbed angular distribution function analysis [27] concluded that the 207-keV transition has a M 1 multipolarity, while the 654-keV one has M 2.…”

“…Because of its half-life, the transition was assigned an (M 2) multipolarity [15]. The 9/2 + spin and parity have been confirmed together with the multipolarities of the cascade transitions in two fragmentation experiments, aiming at measuring the magnetic and quadrupole moment of that state [26,27], respectively. In both cases, 61 Fe was produced at GANIL in a reaction of 64 Ni on a 9 Be target.…”