Circular atoms, i.e., Rydberg atoms with maximum angular momentum, are semiclassical atoms of great interest for Rydberg constant metrology and QED tests. Following a suggestion by Delande and Gay, we have prepared circular atoms by a new method, involving the adiabatic switching of crossed electric and magnetic fields. The method, which is demonstrated for Rydberg states of lithium (principal quantum number $n=20\mathrm{} \mathrm{to} 25$, is applicable over a wide variety of experiment conditions.

• Received 3 May 1988

DOI:https://doi.org/10.1103/PhysRevLett.61.1938