relaxation time

In chemistry and physics, the relaxation phenomenon describes the delay between when an external stress is applied to a system and when that system responds. This occurs when a system, like atoms or molecules, is disturbed from equilibrium, for example, by a sudden change in temperature or pressure, and it takes time to re-establish equilibrium.1

Chemists and physicists study relaxation effects to understand processes that happen very quickly, often in fractions of a second. These effects can be caused by energy redistribution among different states of atoms and molecules or by shifts in the balance of reactants and products in a chemical reaction. Measuring relaxation times provides insights into atomic and molecular structures, as well as the speed and mechanisms of chemical reactions. Relaxation can happen in solids, liquids, or gases and can involve chemical transformations or physical processes like energy transfer between molecular states.123