Interaction with radiation

摘要: α) The dipole approximation. We start from the fundamental formula of radiation theory for probability a spontaneous transition an atom from2 state n to nʹ (energies E and ), with emission one photon. Let k be propagation vector, = | wave number, v nnʹ ωnʹthe “ordinary” “angular” frequency then have Bohr energy relation3 $$\omega _{nn^\prime}\equiv 2\pi \nu ck=\frac{1}{\hbar}(E_n-E_n^\prime)$$ .