A special case of the confluent hypergeometric function of the first kind. It gives the solution to the radial Schrödinger equation in the Coulomb potential (1/r) of a point nucleus (d^2 W)/(d ρ^2) + [1 - (2η)/ρ - (L(L + 1))/ρ^2] W = 0 (Abramowitz and Stegun 1972; Zwillinger 1997, p. 122). The complete solution is W = C_1 F_L(η, ρ) + C_2 G_L(η, ρ).