Treating 𝜓 as a plane wave neglects any interactions between the outgoing electron and the remaining neutral molecule. One solution (without introducing a dipole moment, yet) is to replace the spherical Bessel functions 𝑗 ℓ 𝑘𝑟 in eqn (4) with Coulomb radial functions 𝑅 ℓ 𝑘𝑟, 𝜂 that account for an electrostatic interaction: (9) where Γ is the Gamma function, and 1F1 is the confluent hypergeometric function of the first kind.