Electronic Excitation: Electronic excitation occurs when a molecule absorbs energy and an electron moves from its ground state (lowest energy level) to an excited state (higher energy level). This transition is responsible for many chemical reactions.
Vibrational Modes: Vibrational modes are specific patterns of motion exhibited by atoms within a molecule. During molecular transitions, vibration modes can change as bonds stretch or bend.
Absorption Spectrum: An absorption spectrum is a graph that shows the wavelengths of light or radiation absorbed by a substance. It can provide information about the energy transitions occurring in molecules.