Spherical Bessel function of the second kind
= Spherical Bessel function of the second kind
{title2=$n_\ell(z)$}
= Spherical Neumann function
{synonym}
The spherical second-kind function is $n_\ell(z)=\sqrt{\pi/(2z)}Y_{\ell+1/2}(z)$. Together with the first-kind <Spherical Bessel function>, it spans the radial free-wave solutions; $n_\ell(z)\sim-\cos(z-\ell\pi/2)/z$ at large positive $z$.