LAUSR

Recently the lifetime of the excited 3d94s22D3/2 in Ni- was measured to be 15.1±0.4 s [Phys. Rev. A 93, 012512 (2016)2469-992610.1103/PhysRevA.93.012512]. This deviates from results from nonrelativistic, within the LS-approximation, calculations for this forbidden magnetic-dipole transition of 18.88 s [J. Phys. B 50, 025001 (2017)JPAPEH0953-407510.1088/1361-6455/50/2/025001]. We here present elaborate and fully relativistic multiconfiguration Dirac-Hartree-Fock calculations, to explore this difference. Our calculated transition energy 1485.65cm-1 is in excellent agreement with the experimental 1485±3cm-1 [Phys. Rev. A 58, 2051 (1998)PLRAAN1050-294710.1103/PhysRevA.58.2051]. However the lifetime of 18.86 s, while agreeing well with the nonrelativistic analytical value, deviates from experiment by 25%. The uncertainties of our calculated wavelength and lifetime are estimated to be better than 0.1% and 1%, respectively. In spite of including a careful investigation of contributions from correlation as well as higher-order relativistic effects, we cannot find any explanation from the structure theory for this deviation. (Less)