This amount of energy, i.e., wavelength, is specific to a particular electron transition in a particular element.

There are many possible electron transitions for each atom, and each transition has a specific energy difference.

As a bound electron transitions between different energy levels of an atom, it will absorb or emit photons at characteristic frequencies.

The change electron spin is "forbidden" by the quantum mechanical rules of electron transition.

In ferromagnets, it occurs due to electron transitions between the unsplit 4s and split 3d bands.

A quantum leap is an atomic electron transition between quantum states.

Refers to the appearance of spectral lines representing electron transitions.

The rule originates from a quantum mechanical selection rule that, during an electron transition, parity should be inverted.

After absorption and re-emission of the energy, many wavelengths may emerge due to Stokes shift and various electron transitions.

Vince Calder Peter, Although I would just call it an "electron transition", you hit the nail on the head.