Ground-state Lamb shift for hydrogenlike uranium measured at the ESR storage ring

Abstract

The Lyman \ensuremath{\alpha} transitions of hydrogenlike uranium associated with electron capture were measured in collisions of stored bare ${\mathrm{U}}^{92+}$ ions with gaseous targets at the storage ring ESR. By applying x-ray--particle coincidence techniques the ground-state transition energies in the rest frame could be determined with a precision of about 600 ppm. The experimental result is in excellent agreement with the theroretical prediction for the ground-state Lamb shift in hydrogenlike uranium and is already sensitive to the 2s Lamb shift.