Flexi Says: Saturated hydrocarbons are hydrocarbons that contain only sigma bonds between carbon atoms and between carbon and hydrogen atoms. When the electrons present in sigma bonding orbital absorbs energy similar to UV-visible region, it gets excited to the higher energy sigma antibonding molecular orbital. The sigma bonds are very strong therefore, high energy is required for sigma-sigma star transition and that is why this electronic transition is studied to understand the mechanism of the photochemical reaction using UV-Visible spectroscopy.
