Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Ramsauerâ€“Townsend effect, also sometimes called the Ramsauer effect or the Townsend effect, is a physical phenomenon involving the scattering of low-energy electrons by atoms of a noble gas. Since its explanation requires the wave theory of quantum mechanics, it demonstrates the need for physical theories more sophisticated than those of Newtonian physics. When an electron moves through a gas, its interactions with the gas atoms cause scattering to occur. These interactions are classified as inelastic if they cause excitation or ionization of the atom to occur and elastic if they do not.