  The differential expression $L_m=-\partial_x^2 +(m^2-1/4)x^{-2}$ defines a
self-adjoint operator H_m on L^2(0;\infty) in a natural way when $m^2 \geq 1$.
We study the dependence of H_m on the parameter m, show that it has a unique
holomorphic extension to the half-plane Re(m) > -1, and analyze spectral and
scattering properties of this family of operators.
