Proton radius mystery deepens as deuterium measurement comes up short. Improving mass accuracy. In a commentary written to accompany the research, Niels Madsen of Swansea University in the UK points ...

A new detector sensitive to low-mass dark matter particles too light for current experiments to see has been proposed by physicists in the US. Built around a bath of superfluid helium-4, the device ...

Helium is the simplest multi-body atom. Its energy levels can be calculated with extremely high precision only relying on a few fundamental physical constants and the quantum electrodynamics (QED ...

An elusive type of atom known as pionic helium has been directly excited by laser light for the first time. The work establishes a promising experimental platform for probing fundamental physics ...

Laser physicists have captured an atomic-level event – an electron being ejected from a helium atom after being struck by a photon – with an accuracy of a trillionth of a billionth of a second ...