Can the spin quantum number spontaneously change from + to -? If so, what is the energy of the transition?
The spin of an electron can change when acted upon by the fields of other electrons or by a magnetic field. In an atom the electron spins interact with the electron velocities, which is called the spin-orbit interaction. Direct interaction between spins also exists, and both effects are to lowest order proportional to (v/c)^2 (hence relativistic). The energies of the transitions depend on the atom and the states involved, but you can find more information under the name “fine structure”, e.g. in Wikipaedia here: http://en.wikipedia.org/wiki/fine_struct… When the spin interaction is taken into account, then only the total angular momentum (total orbital+total spin) is a “good” quantum number. I don’t don’t understand your statement about the orbital angular momentum being “kept constant”. In that case it is not a constant, nor is the spin; only the total angular momentum is. The spin of an isolated electron does no
