2025/02/08 by Cheung, Charles, Porsev, Sergey G., Filin, Dmytro +7
#Atomic Physics (physics.atom-ph) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2502.05386
The Ni12+ ion features an electronic transition with a natural width of only 8 mHz, allowing for a highly stable optical clock. We predict that the energy of this strongly forbidden 3s2 3p4 3 P2 → 3s2 3p4 3 P0 electric quadrupole transition is 20081(10) cm-1. For this, we use both a hybrid approach combining configuration interaction (CI) with coupled-cluster (CC) method and a pure CI calculation for the complete 16-electron system, ensuring convergence. The resulting very small theoretical uncertainty of only 0.05% allowed us to find the transition experimentally in a few hours, yielding an energy of 20078.984(10) cm-1. This level of agreement for a 16-electron system is unprecedented and qualifies our method for future calculations of many other complex atomic systems. While paving the way for a high-precision optical clock based on Ni12+, our theory and code development will also enable better predictions for other highly charged ions and other complex atomic systems.