respectively, where 𝑟 𝑒 = Δ𝑥 2 ⁄ [m] is the radius corresponding to a spherical mass of finite size and (𝐸 * -𝐸) is the difference in energy levels between the excited state 𝐸 * and the ground state 𝐸 within the atom of a specified element. Setting 𝑁 Po = 𝑁 Re 𝑁 f and rearranging yields the expression