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The identity that Krall uses is:

[itex]\int d\vec{x} \frac{ e^{- x^2 }}{ \left| \vec{x}-\vec{y} \right| } = \frac{\pi^{3/2}\text{Erf}\left[ y \right]}{y} [/itex]

Where x,y denote the magnitude of the x,y vectors and Erf is the error function. The integral on x is over all 3D space.

I suppose in the end I want to know how to show the identity is true. It would also be helpful is someone has seen this or similar integrals in table of integrals. Resources that are related are welcomed. I would also just like some more ideas on how to attack it.

My best attempts were using:

spherical coordinates (with z-axis along y-direction)

differentiating under the integral with respect to magnitude if y

I'm in my 3rd year of grad. school in physics so hopefully you won't need to spell it all out for me to follow. Thanks!