Selection rules mentioned in all books on atomic physics state that for example orbital quantum number must change by 1 when electron does transition between energy states of an atom. Does this apply only for radiative transitions (that is transitions that involve photon emission/absorption) or does it apply generally for any other type of transitions (eg. collisions)?

What I am basically trying to clear up in my head is: when I see "selection rules" in a textbook, should I immediately associate that with radiative transitions only or should I also think about other types of transitions?


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As far as I can tell, "selection rules" is terminology applicable only to radiative transitions. The rules originate in the multiple expansion of the potential.

Dipole transitions change angular momentum by $0$ or $\hbar$ because the dipole moment is the $L=1$ multipole. Quadrupole transitions change angular momentum by up to $2\hbar$ because the quadrupole moment is the $L=2$ multipole.

In atoms dipole transitions are dominant but other transitions are also possible. In nuclear physics many transitions are quadripolar in nature, especially in rotational bands. Thus it is not so much that "angular momentum much change by $1$" in atomic transitions but rather that the quadrupole transitions are much much less intense than dipole transitions in atoms. Higher multipole beyond $L=1$ will be seen in atoms where some dipole transitions are forbidden.


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