Electromagnetic Backgrounds and Angular-Momentum Barriers in Gravitomagnetic Searches with Hydrogen-Like Ions
Researchers applied Generalized King Plot methods to search for gravitomagnetic spin-quadrupole coupling in highly charged ions like molybdenum. They found that a hierarchy of four electromagnetic barriers limits sensitivity, setting a first laboratory bound on the gyrogravitational ratio |χ−1| ≲ 10^8–10^9 for this signal.