# Complex integrals and residues

I have a question. I try to integrate this function:

Integrate[Exp[I k z]*Exp[-Sqrt[k^2 - A^2]x]*Exp[-k^2*L^2/4]/Sqrt[k^2 - A^2],
{k, -Infinity, -A}]


But Mathematica doesn't want to give an answer. It just prints me my integral.

The same story I have when I try to calculate the residue of this function at the infinity point, for example.

What's wrong?

Thanks.

• Nothing is wrong with the syntax, I think it's because this integration doesn't have a analytic solution (at least Mathematica doesn't know it), consider NIntegrate if a numeric solution is enough for you. – xzczd May 21 '14 at 7:37
• You should first take a look e.g. here; How to calculate contour integrals with Mathematica?, perhaps this can be a simpler help: Paths integrals in the complex plane. – Artes May 21 '14 at 9:17