\[W_{-\kappa,\mu}\left(4\kappa x\right)=\frac{\sqrt{8/\pi}e^{\kappa}}{\kappa^{%
\kappa-\frac{1}{2}}}\left(\frac{x\zeta}{1+x}\right)^{\frac{1}{4}}K_{2\mu}\left%
(4\kappa\zeta^{\frac{1}{2}}\right){\left(1+O\left(\kappa^{-1}\right)\right)},\]