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Register a new userGround-state $g$ factor of highly charged $^{229}$Th ions: an access to the M1 transition probability between the isomeric and ground nuclear states
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A method is proposed to determine the $M1$ nuclear transition amplitude and hence the lifetime of the nuclear clock transition between the low-lying ($sim 8$ eV) first isomeric state and the ground state of $^{229}$Th from a measurement of the ground-state $g$ factor of few-electron $^{229}$Th ions. As a tool, the effect of nuclear hyperfine mixing (NHM) in highly charged $^{229}$Th-ions such as $^{229}$Th$^{89+}$ or $^{229}$Th$^{87+}$ is utilized. The ground-state-only $g$-factor measurement would also provide first experimental evidence of NHM in atomic ions. Combining the measurements for H-, Li-, and B-like $^{229}$Th ions has a potential to improve the initial result for a single charge state and to determine the nuclear magnetic moment to a higher accuracy than that of the currently accepted value. The calculations include relativistic, interelectronic-interaction, QED, and nuclear effects.
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The magnetic hyperfine (MHF) structure of the $5/2^+$(0.0 eV) ground state and the low-lying $3/2^+$(7.8 eV) isomeric state of the $^{229}$Th nucleus in highly charged ions Th$^{89+}$ and Th$^{87+}$ is calculated. The distribution of the nuclear magnetization (the Bohr-Weisskopf effect) is accounted for in the framework of the collective nuclear model with the wave functions of the Nilsson model for the unpaired neutron. The deviations of the MHF structure for the ground and isomeric states from their values in the model of point-like nuclear magnetic dipole are calculated. The influence of the mixing of the states with the same quantum number $F$ on the energy of sublevels is studied. Taking into account the mixing of states, the probabilities of the transitions between the components of MHF structure are found.
The paper presents the current status of the theory of bound-electron g factor in highly charged ions. The calculations of the relativistic, QED, nuclear recoil, nuclear structure, and interelectronic-interaction corrections to the g factor are reviewed. Special attention is paid to tests of QED effects at strong coupling regime and determinations of the fundamental constants.
We present direct observation of the M1 transition between the fine structure splitting in the 4f13 5s2 5p6 2F ground state of W VIII. The spectroscopic data of few-times ionized tungsten ions are important for the future ITER diagnostics, but there is a serious lack of data. The present study is part of an ongoing effort to solve this lack. Emission from the tungsten ions produced and trapped in a compact electron beam ion trap is observed with a Czerny-Turner visible spectrometer. Spectra in the EUV range are also observed at the same time to help the identification of the previously-unreported visible lines. The observed wavelength 574.47 pm 0.03 nm (air), which corresponds to the fine structure splitting of 17402.5 pm 0.9 cm-1, shows reasonable agreement with the previously reported value 17410 pm 5 cm-1 obtained indirectly through the analysis of EUV spectra [Ryabtsev et al., Atoms 3 (2015) 273].
A detailed-level collisional-radiative model for the M1 transition spectrum of the Ca-like W$^{54+}$ ion as observed in an electron beam ion trap (EBIT) was constructed based on atomic data calculated by the relativistic configuration interaction method and distorted wave theory. The present calculated transition energy, rate and intensity of W$^{54+}$ M1 transitions are compared with previous theoretical and experimental values. The results are in reasonable agreement with the available experimental and theoretical data. The synthetic spectrum explained the EBIT spectrum in the 12-20 nm region, while a new possibly strong transition has been predicted to be observable with an appropriate electron beam energy. The present work provides accurate atomic data that may be used in plasma diagnostics applications.
The electric-field-dependent $g$ factor and the electron electric dipole moment (eEDM)-induced Stark splittings for the lowest rotational levels of $^{207,208}$PbF are calculated. Observed and calculated Zeeman shifts for $^{207}$PbF are found to be in very good agreement. It is shown that the $^{207}$PbF hyperfine sublevels provide a promising system for the eEDM search and related experiments.
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