Theoretical Study On The Atomic Properties Of The Highly Charged Nickle Ions For Optical Clock Candidates

The optical clocks with extraordinary precision allow not only for improving the measurement accuracy of time and frequency,but also for advancing the frontier research of fundamental physics.The fractional uncertainties of a few parts in 10-18,even in 10-19,have been achieved in current optical clocks,which are based on the electronic transitions in atoms and singly charged ions.Comparing with atoms and singly charged ions,the highly charged ions(HCIs)possess optical transitions that can be extremely insensitive to the external perturbations and sensitive to the variation of the fine structure constant α.Therefore,HCIs have been suggested as promising candidates for the next generation of ultraprecise optical clocks.The HCI clocks attracted considerable attention in recent years since the novel optical clock belongs to a new frontier research area.Both theoretical and experimental researches on the HCI clocks are still in the initial exploration stage.On the theoretical side,a large number of suitable clock HCI candidates have been proposed.But,the theoretical study of the atomic properties which are indispensable for experiments for these HCI clocks,are scarce.Experimentally,the successes in sympathetic cooling and quantum logic spectroscopy of the Ar13+ and Be+ ions have been achieved,which paved way for HCI optical clocks.Therefore,the theoretical study of the atomic properties for HCIs is indispensable for selecting optical clock candidates and experimentally building novel optical clocks.In this thesis,we studied the atomic properties of four adjacent charge states of nickel HCIs by using the multiconfiguration Dirac-Hartree-Fock(MCDHF)method.Based on the investigation of the level structure of the Ni11+,Ni12+,Ni14+ and Ni15+ ions,we recommended six optical transitions(four Magnetic-dipole(M1)transitions and two electric-quadrupole(E2)transitions)for high-accuracy optical clocks.Moreover,the atomic properties relate to these six transitions were calculated.The main studies are as follows,(1)The energies of the low-lying states of the Niq+(q=11,12,14 and 15)ions and the transition properties between these states were studied.Based on the discussion of the influences of the electronic correlation effects,Breit interaction,and QED effect on the concerned physical quantities,suitable computational models were constructed.The transition energies and probabilities of the transitions involving the ground states of Ni11+,12+,14+,15+ions,and the lifetimes of low-excited states are calculated.The calculated results in this thesis are in good agreement with the latest experiment and theoretical and experimental results in available literature,which confirmed the reliability of the computational models.Furthermore,using the calculated results,we evaluated the natural linewidth and quality factor of these transitions,and the sensitivity coefficient for the variation of the fine structure constant a.We recommended six clock transitions with higher quality factors and sensitive to a variation.They are:·M1 transition 3s23p5 2P1/2 o-2P3/2 o for Ni11+,·M1 transition 3s23p4 3p1-3P2 and E2 transition 3s23p4 3p0-3P2 for Ni12+,·M1 transition 3s23p2 3p1-3P0 and E2 transition 3s23p2 3P2-3P0 for Ni14+,·M1 transition 3s23p 2P3/2 0-2P1/2 0 for Ni15+.(2)The hyperfine structures of 61Ni11+,12+,14+,15+ ions and the sensitivities of clock transition frequencies to the magnetic field and electric field gradient were studied.In order to calculate the hyperfine interaction constants,Lande g factors and electric quadrupole moments of the states relate to clock transitions,we analyzed the effect of the electronic correlation effect,Breit interaction and QED effect on these physical quantities.Using our calculation results and achievable experimental conditions,the electric quadrupole frequency shifts and Zeeman frequency shifts of the clock transitions were discussed.As a result,we recommend developing a nickel ion optical clock by using 61Ni.Clock transitions with a negligible quadrupole shift were selected between the hyperfine levels of the 61 Ni11+,12+,14+,15+ ions.At the same time,we found that the quadratic Zeeman shifts should be measured precisely for achieving the uncertainty below the 10-19 level.The calculated results in this work can provide a large number of high-precision atomic parameters for the development of the HCI optical clock experimentally.(3)Role of the hyperfine interaction on the g-factor of clock states were studied.In the weak-magnetic-field approximation,we derived a general expression of hyperfine-induced Lande g-factors.Using this expression and the MCDHF theory the g-factors were calculated for the 3s3p 3P0 o clock state in 27Al+ and 5s5p 3P0 o in 87Sr.Good agreement are found between our calculated results and available experiment results in the literature.The good agreement proved the correctness of our method for dealing with hyperfine interaction and magnetic field interaction in the weak field approximation.On the other hand,it proves the reliability of the computational models for Al+ ion and Sr atom.(4)Hyperfine-mediated effects on the electric quadrupole moments and g-factors of the states relate to clock transitions in 61Ni12+ were studied.The hyperfine-induced electric quadrupole moments and g-factors of the 3s23p4 3P0,1,2 states were calculated in the weak-field approximation.The electric quadrupole frequency shifts and quadratic Zeeman frequency shifts of the clock transitions were evaluated with unprecedented precision.