Charged Atomic Clocks: How to Catch the Exact Time
Ordinary atomic clocks tick when an electron jumps between energy levels. But external fields and jolts can disrupt this rhythm. Highly charged ions, atoms stripped of many electrons, barely notice such disturbances: their electrons sit deep and tight. That makes them ultra-stable 'pendulums.'
The Cf17+ ion is a curium atom that has lost 17 electrons.