Relativistic phenomena that successively grow with nuclear charge

0. Electrostatic Solution

Solution of Schrödinger equation with Coulombic potential. Excited levels are stable and DO NOT decay.

1. Electric Dipole (E1) Radiation

A time-dependent electric dipole moment p=qr couples E and B fields to produce electromagnetic radiation, and excited states can decay.

2. LS Coupling in multielectron atoms

Magnetism couples electron spins to each other (S) and electron orbits to each other (L). They do this separately since in a magnetic field the electron spin precesses at twice the frequency of that of its orbit.

3. Magnetic Dipole (M1) Radiation

A time dependent magnetic dipole moment m=IA causes the total spin S to reorient relative to the total orbital angular momentum L, changing the J of the atom by emission of radiation. The dipole moment depends only on angular coordinates, and the transition is within a non-relativistic nl subshell.

4. Intermediate Coupling (IC)

The large charge of the nucleus causes the field produced by the relative motion of the electron and the nucleus to couple to its spin. Thus the spin-own-orbit interaction becomes competitive with the spin-spin and orbit-orbit interactions, producing a complex coupling somewhere between LS and jj. (L and S cease to be good quantum numbers, and only J is defined.)

5. Relativistic Magnetic Dipole Radiation (Rel. M1)

Because of relativistic effects due to the eccentricity of the orbits, the magnetic dipole moment acquires a radial dependence. (In m=IA, the area of an ellipse is pab, but the path of the current is the circumference of an ellipse, which can only be evaluated numerically as an "elliptic" integral. This differs from the circular orbit case, where a factor of r cleanly cancels in the ratio of pr² with 2pr/v to yield a quantity proportional to the angular momentum operator.)

6. Quantum Electrodynamics (QED)

As aZ increases, so does the flux of virtual photons in the core of the atom. This makes possible many higher order processes such as emission and reabsorption of virtual photons (self-energy corrections), electron-positron pair creation and subsequent annihilation (vacuum fluctuations) and many other processes treated under the rubric "Feynman diagrams."