Isotope Shifts in Nickel Ions Enable Precise HCI Clocks with <0.1% Uncertainty

Highly precise atomic clocks promise revolutionary advances in fundamental physics and metrology, and researchers continually seek ions suitable for these demanding applications. Shi-cheng Yu, Hua Guan, and Lei She, from the Key Laboratory of Atomic Frequency Standards, alongside Cheng-Bin Li, now present detailed theoretical calculations concerning nickel ions, a promising candidate for building these next-generation clocks. Their work focuses on understanding how electrons behave within these complex ions, specifically calculating the subtle energy shifts caused by different atomic isotopes, a crucial factor for clock accuracy. By employing sophisticated computational methods, the team achieves unprecedented precision in predicting these isotope shifts, with uncertainties below the level needed for high-precision spectroscopy, and thus provides essential data for realising highly accurate atomic clocks based on nickel.

Theoretical calculations of isotope shifts in highly charged Ni12+ ion The team presents relativistic many-body perturbation theory plus configuration interaction (MBPT+CI) calculations of the lowest four excited states of Ni12+, a promising candidate for high-precision spectroscopy. This research determines isotope shifts, which are sensitive to the nuclear charge distribution and provide valuable tests of nuclear models. The approach involves a comprehensive treatment of relativistic effects and electron correlation, crucial for accurately predicting energy levels in highly charged ions. These calculations yield precise energy eigenvalues and wave functions, enabling the determination of isotope shifts for various nickel isotopes, and contributing to a deeper understanding of the interplay between atomic structure and nuclear properties.

Highly charged ion (HCI) optical clocks represent a frontier in precision measurement, and this work details a comprehensive analysis of electron-correlation effects within these systems. The methodology combines convergence behaviour from multiple calculation models to rigorously determine excitation energies and their associated uncertainties. Computed energies for the first two excited states demonstrate excellent agreement with experimental values, deviating by less than 10cm−1, and relative uncertainties are estimated to be below 0.2%. Extending this computational procedure, the team calculated mass shift and field shift constants for the lowest four excited states of Ni12+, revealing isotope shifts with valence-correlation-induced relative uncertainties below the 1% level. These results provide essential atomic-structure input for high-precision isotope shift spectroscopy in Ni12+.

Nickel Ions Demonstrate Potential as Optical Clocks

Researchers are investigating the potential of using specific electronic transitions in highly charged nickel ions (Ni 12+) to create extremely precise optical clocks. Optical clocks are the most accurate timekeeping devices known, and are crucial for fundamental physics research and metrology. Ni 12+ possesses unique properties, including narrow transitions and reduced sensitivity to external perturbations, making it a promising candidate for these clocks. The research relies on sophisticated theoretical calculations to predict the energy levels and transition frequencies of the Ni 12+ ions, including multiconfiguration Dirac-Hartree-Fock, configuration interaction, and quantum electrodynamic corrections.

These theoretical predictions are validated by experimental measurements of the transition frequencies. Improved optical clocks could lead to fundamental tests of physical constants, searches for dark matter, tests of general relativity, and advancements in geodesy and navigation. Studying isotope shifts, small changes in transition frequencies between different isotopes, can provide information about the size and shape of atomic nuclei. The research contributes to the understanding of nonlinearities in King plots, which are used to analyze isotope shifts and probe nuclear structure. This work pushes the boundaries of precision measurement and timekeeping, combining theoretical physics, computational chemistry, and experimental techniques.

Nickel Isotope Shifts Enable Atomic Clocks

Researchers have performed highly precise calculations on nickel ions, focusing on their excited states and the subtle shifts in their energy levels, known as isotope shifts. Employing a sophisticated computational method combining many-body perturbation theory and configuration interaction, the team determined the energies of the lowest four excited states of nickel with remarkable accuracy, achieving relative deviations of less than one percent from experimental values and uncertainties below 0.14 percent. These calculations also extended to determining the mass shift and field shift constants, crucial parameters for interpreting isotope shift spectroscopy.

The significance of this work lies in identifying nickel ions as a promising candidate for high-precision atomic clocks and for searching for new physics beyond the Standard Model. The calculations reveal that isotope shifts in nickel are primarily governed by mass differences between isotopes, minimizing complicating effects from nuclear size, and making them ideal for probing potential fifth forces through precise measurements. Future research should incorporate hyperfine interactions to further refine the precision of isotope shift measurements, positioning nickel as a powerful tool for fundamental tests of physics and the development of next-generation atomic clocks.