Rydberg atom
![Figure 1: Energy levels in atomic lithium showing the Rydberg series of the lowest 3 values of orbital angular momentum converging on the first ionization energy.](/Images/godic/202502/08/Lithium_levels0055.png")
![Figure 2. A comparison of the potential in a hydrogen atom with that in a Rydberg state of a different atom. A large core polarizability has been used in order to make the effect clear. The black curve is the Coulombic 1/r potential of the hydrogen atom while the dashed red curve includes the 1/r4 term due to polarization of the ion core.](/Images/godic/202502/08/CorePolarizationPotential.svg0055.png")
![Figure 3. Semiclassical orbits for n=5 with all allowed values of orbital angular momentum. The black spot denotes the position of the atomic nucleus.](/Images/godic/202502/08/Sommerfeld_ellipses.svg0056.png")
![Figure 4. Computed energy level spectra of hydrogen in an electric field near n=15.[14] The potential energy found in the electronic Hamiltonian for hydrogen is the 1/r Coulomb potential (there is no quantum defect) which does not couple the different Stark states. Consequently the energy levels from adjacent n-manifolds cross at the Inglis-Teller limit.Figure 5. Computed energy level spectra of lithium in an electric field near n=15.[14] The presence of an ion-core that can be polarized and penetrated by the Rydberg electron adds additional terms to the electronic Hamiltonian (resulting in a finite quantum defect) leading to coupling of the different Stark states and hence avoided crossings of the energy levels.](/Images/godic/202502/08/Hfspec10056.jpg")
A Rydberg atom is an excited atom with one or more electrons that have a very high principal quantum number. These atoms have a number of peculiar properties including an exaggerated response to electric and magnetic fields, long decay periods and electron wavefunctions that approximate, under some conditions, classical orbits of electrons about the nuclei. The core electrons shield the outer electron from the electric field of the nucleus such that, from a distance, the electric potential looks identical to that experienced by the electron in a hydrogen atom.