Atoms in strong crossed electric and magnetic fields: Evidence for states with large electric-dipole moments

This paper reports on the evidence for large permanent electric-dipole moments of Rydberg atoms in crossed electric and magnetic fields. It was found that the dipole moments have a large value if the scaled electric-field strength {ε}=EB^-4/3 has the value {ε}{}0.75 (with electric- and magnetic-field strengths E and B in atomic units). The experimental technique employed to determine the atomic dipole moment was to add a slight inhomogeneity to the electric field and to measure the deflection of the atoms, this deflection being proportional to the field inhomogeneity and the atomic dipole moment. In order to discuss the experimental results, different theoretical approaches to the E×{}B problem are reviewed. The occurrence of Rydberg atoms with large dipole moments can be explained as being caused by a distinct type of classical orbit.