Barium Circular Atoms Prepared by the Crossed-Field Method

Abstract
Circular two-electron atoms, i.e. Rydberg atoms where the angular momentum of one of the valence electrons is maximum, have been prepared in barium (n = 21) by using the adiabatic crossed-field method already tested in alkali atoms. This simple and versatile method proves to be very efficient for heavy atoms with large quantum defects. Circular alkaline-earth atoms represent a decisive step for the preparation of doubly-excited Rydberg states with long autoionization lifetimes.