Nuclear Moments and Deformation Change inA184ug,m

Abstract

Resonance ionization spectroscopy (RIS) was performed on desorbed Au, and the complete hyperfine spectrum of both isomeric and ground states of the short lived 184 Au nucleus has been recorded from the 5d 10 6s 2 S 1͞2 ! 5d 10 6p 2 P 3͞2 optical transition. The nuclear moments of both states and the mean square charge radius changes were measured. The magnetic moments were determined to be m 184g Light gold isotopes belong to a mass region where drastic changes in the nuclear charge radius have been measured by laser spectroscopy. Such alterations have shown alternating shape transitions and deformation changes between neighboring isotopes. This was observed in mercury [1,2], gold [3][4][5], and to a lesser degree in platinum isotopes [6,7]. Different deformations have also been observed in the states of the same nucleus. The best example is 185 Hg where the large radius difference measured between its ground and isomeric state [8] has shown a prolate-oblate shape coexistence which was confirmed later from g-ray spectroscopic studies [9,10].In this context, the doubly odd nucleus 184 Au with its isomeric state at 68 keV excitation energy [11,12] is particularly interesting to investigate since it is located in the middle of this transitional region [13,14]: States corresponding to prolate and oblate or triaxial shapes coexist in 183,185 Au [9,15,16] and 185 Hg, while 183 Pt is prolate in all its low energy states [17][18][19]. Several nuclear spectroscopy studies were performed on 184 Au, and it has been established that (i) a shape coexistence is excluded at low excitation energy [20], and (ii) the spin and parity are 5 1 for the ground state and 2 1 for the isomer with the following proton-neutron ͑p ≠ n͒ configurations: ph 9 2 ≠ n 7 2 ͓514͔ and ph 9 2 ≠ n 1 2 ͓521͔, respectively [21]. Furthermore, calculations using rotor 1 one-quasiparticle and rotor 1 two-quasiparticle coupling models were performed on the N 105 isotones 183 Pt, 182 Ir [22], 185 Hg, and 184 Au [23]. They show that the relative energy location of the 5 1 and 2 1 states suggests a deformation change, either between 184 Au g and 184 Au m or between 184 Au and its neighboring isotopes. Therefore, the determination of the quadrupole moment in both isomer and ground states, as well as the change in the mean square charge radius between them, is crucial to fully characterize their nuclear shape. Moreover, a measurement of the magnetic moments of the two states will allow a clear confirmation of the p ≠ n configurations. In addition, the p ≠ n coupling scheme can be defined from the quadrupole moment values.In this Letter, we present optical measurements on 184 Au. The hyperfine structure is measured providing the magnetic A and electrostatic B hyperfine constants of the levels involved in the atomic transition as well as the isomeric shift. A is related to the magnetic moment m I , and B to the spectroscopic quadrupole moment Q s . The isomeric shift, which is the displacement of the centers of gravity of the two hyperfine spectra, determines the...

Hyperfine anomaly in gold and magnetic moments of Iπ=11/2− gold isomers

“…The magnetic moments of 183 Au, 184 Au g , 184 Au m were determined by the standard prescription with ε = 0 [57,58] but the data on a 6p are missing and it is impossible to apply our procedure to calculate the RHFA. Keeping in mind the possible failure of the standard prescription for these nuclei, the uncertainties ascribed in Refs.…”

Penning-trap mass spectrometry and mean-field study of nuclear shape coexistence in the neutron-deficient lead region

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