The change in electronic excitation represents both a potential and a kinetic energy term in classical physics, but there is no simple correspondence to classical physics terms, when you are looking at quantum systems. All we really care about is the total energy difference between electronic states. Those energy differences correspond to the energies at which photons can be absorbed and emitted. In the presence of magnetic fields there are also energy terms that stem from the spins and angular momenta of electrons and of the spins of the nucleons. The magnetic fields can be either external, or generated by the configuration of electrons inside the molecules and atoms, themselves. Finally, spins can interact with the dipole fields of other spins.
All of these spin interactions can add tiny variations to the frequencies of absorption and emission, and they give very important clues to the chemical composition of molecules, so much so, that magnetic resonance has become one of the chemist's workhorse methods for molecular structure determination.
In addition, the interaction between the photon spin and the molecules can lead to polarization effects. The polarization of photons scattering off these molecules can change or emitted light can be polarized.