where u CM is the versor of the nucleus momentum, E CM = P 2 /2M is the kinetic energy of the center of mass, R = (m N r N + m e r e )/(m N + m e ) is the coordinate of the center of mass before photon-atomic electron interaction, M is the total mass of the atom, m e is the mass of the electron and m N is the mass of the nucleus, P is the momentum of the center of mass, = h/2π where h is the Palnck constant, and u CM is the versor of the momentum of the nucleus. Then, the photon incomes to the atomic electron, which jumps from the fundamental state into an excited energy state, and then it jumps down to the fundamental state, with the emission of a new photon. The fundamental state function, after this interaction, solution of the Schrödinger equation, can be obtained by the quantum mechanics :