ABSTRACT

This chapter focuses on the examination of the source of the radiated energy after examining the radiation fields. Energy and momentum are transferred from the charges to the electromagnetic field; the rate at which the current does work on the field. It discusses dipole radiation produced by a small charge distribution, for which the nonrelativistic approximation is valid, that is, all particle speeds are small compared to the speed of light. The Hamiltonian form is appropriate for small systems and has application in both atomic and nuclear physics. It is called the Darwin Hamiltonian when it is applied classically, and the Breit Hamiltonian when it is applied quantum mechanically (with an accompanying re-expression in terms of Dirac matrices).