How do electron-electron repulsions impact the electronic spectrum?

Electron-electron repulsions significantly influence the electronic spectrum by leading to multiple absorption peaks. When there are electrons present in an atom or a molecule, their interactions with each other can cause a splitting of energy levels due to the repulsive forces between negatively charged electrons. This splitting creates distinct energy levels rather than a single level, resulting in multiple transitions when energy is absorbed.

Each transition corresponds to a specific absorption peak in the electronic spectrum. When a photon with the right energy matches the energy difference between these split levels, the electron can be promoted to a higher energy state. The presence of multiple energy levels due to electron-electron interactions allows for various possible electronic transitions, hence producing multiple absorptions in the spectrum.

By understanding this concept, one can better predict and analyze the electronic spectra of different substances, noting that the broadening of peaks or the presence of numerous peaks is often tied to the repulsion effects among electrons.