Perturbing Hamiltonian for optical absorption
Here, we explain the origin of the relation
for the perturbing Hamiltonian when we have an electromagnetic field, described by the vector potential A, interacting with an electron. There are four stages to this derivation. First, we need to write the classical Hamiltonian for this interaction and show why it is correct classically. This Hamiltonian is, for a particle of charge e
Second, we have to change this classical Hamiltonian into a quantum mechanical ...