= Atomic transition
An <atomic transition> changes an <atom> between <quantum states>. For states with <energies> $E_i,E_f$, a single-photon resonant transition obeys $h\nu=|E_f-E_i|$. <Absorption> raises the atomic <energy>; spontaneous or stimulated <emission> lowers it.
<Energy> matching is necessary but not sufficient: the interaction <matrix element> and <selection rules> determine whether a transition is allowed and how strong it is. For an electric-dipole transition between angular-momentum states, <polarization> determines which <magnetic sublevels> can be coupled. Transitions therefore provide information about both level <energies> and state <symmetry>.
Back to article page
