Abstract
Hyperfine-structure constants for the 6s2S1/2 and 6p2P1/2 atomic states of the Iπ=11/2− gold isomers Aum177,191,193,195 have been measured at CERN-ISOLDE, using the in-source laser resonance-ionization spectroscopy technique. From the measured hyperfine constants the differences between hyperfine anomalies for these atomic states have been deduced. These differential hyperfine anomaly values have been used to determine the 6s-state hyperfine anomaly relative to the stable Au197 with advanced atomic calculations. Magnetic dipole moments for the gold isomers in question have been deduced, taking into account the corresponding relative hyperfine-anomaly values. It has been shown that the commonly used prescription for the extraction of the magnetic moment values for the gold isotopes should be reconsidered. The magnetic moments calculated by this prescription have been reevaluated by properly accounting for the hyperfine anomaly, which is as large as 10% for several gold isotopes.
Highlights
INTRODUCTIONThe magnetic dipole moment μA for a nucleus of mass number A and with a spin I can be calculated using the following expression: μA
The magnetic dipole moment μA for a nucleus of mass number A and with a spin I can be calculated using the following expression: μA = μrefIA Iref aA aref (1)where a is a magnetic hyperfine constant and the subscript “ref” denotes a reference isotope with known μ and a values.Eq (1) is based on a pointlike approximation for the charge and magnetization in the nucleus
The finite size of the nucleus leads to the deviation of the hyperfine constant from the pointlike value apt
Summary
The magnetic dipole moment μA for a nucleus of mass number A and with a spin I can be calculated using the following expression: μA. Ekström et al [9] proposed a procedure (referred to as the standard prescription in the following text) to account for the large RHFA in gold isotopes, which was used in all subsequent works devoted to hyperfine-structure (hfs) measurements in gold isotopes. This procedure is not well grounded, as will be shown in Sec. II of the present study. A calculation of the quantity aptI/μ using Eq (2) with this absolute HFA value gives aptI/μ = 29005 MHz/μN Correspondingly, the standard prescription for extracting the magnetic moment value from the measured hfs constant of the gold isotope is μ aI 29005. In the Appendix the same procedure has been applied for some previously studied gold isotopes
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