Selection rules are a set of rules that determine which transitions or interactions are allowed between different energy levels in an atom or molecule. They are based on conservation laws, such as conservation of energy, momentum, and angular momentum.
Selection rules determine which transitions between energy levels are allowed, so they directly impact the wavelengths of light that are emitted or absorbed by atoms or molecules. Only transitions that follow the selection rules are allowed, resulting in specific spectral lines.
Quantum numbers are values used to describe the energy states of electrons in an atom or molecule. They include the principal quantum number, orbital angular momentum quantum number, magnetic quantum number, and spin quantum number. Selection rules are based on these quantum numbers and their relationships to each other.
Selection rules play a crucial role in interpreting the spectra of atoms and molecules. By following the selection rules, we can determine which transitions are allowed and which are forbidden, providing valuable information about the energy levels and electronic structure of the system.
In some cases, selection rules can be broken or violated, resulting in forbidden transitions that are usually weak or occur at longer wavelengths. This can happen due to external perturbations or deviations from ideal conditions and can provide insight into the underlying physical processes at play.