$\delta =-iϵ\nu ^{2}$
$\nu \neq 0$

$\left\{\begin{matrix}\nu =\left(-\frac{1}{2}-\frac{1}{2}i\right)ϵ^{-\frac{1}{2}}\sqrt{2\delta }\text{; }\nu =\left(\frac{1}{2}+\frac{1}{2}i\right)ϵ^{-\frac{1}{2}}\sqrt{2\delta }\text{, }&\delta \neq 0\text{ and }ϵ\neq 0\\\nu \neq 0\text{, }&ϵ=0\text{ and }\delta =0\end{matrix}\right.$