On the eigenvalues in problems with spherical symmetry
Edward Charles Titchmarsh · Proceedings of the Royal Society of London A Mathematical and Physical Sciences · 1958
Abstract It is shown that the eigenvalues associated with the equation ∇2ψ + { λ — q(r)} = 0, where q(r) is a function of r only and tends to infinity as r → ∞, are the roots of equations of the form ∫R0 { λ — q(r)}½ dr = (½l + n + ¾) π + δn, where l and n are integers, and δn is small when n is large.