# Evaluating an integral combining a Bessel function with some other functions [closed]

How can I evaluate the integral of $$j_1 ^2(x)\exp(-bx)/x$$ from 0 to ∞?

## closed as off-topic by Daniel Lichtblau, Roman, garej, Edmund, MarcoBJul 1 at 16:34

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## 1 Answer

If you mean the Bessel function $$J_1(x)$$:

Assuming[b > 0,
Integrate[BesselJ[1, x]^2*Exp[-b x]/x, {x, 0, ∞}]]


(π + b^2 EllipticE[-4/b^2] - (4 + b^2) EllipticK[-4/b^2])/(2π)

If you mean the spherical Bessel function $$j_1(x)$$, it's a bit harder:

J[b_, x_] = Integrate[SphericalBesselJ[1, x]^2*Exp[-b x]/x, x];
Assuming[b > 0,
Limit[J[b, x], x -> ∞] - Limit[J[b, x], x -> 0, Direction -> "FromAbove"] // FullSimplify]


1/96 (-4 (-6 + b^2) - 32 b ArcTan[2/b] + b^2 (12 + b^2) (-2 Log[b] + Log[-2 I + b] + Log[2 I + b]))

The last line can be simplified to

1/96 (-4 (-6 + b^2) - 32 b ArcTan[2/b] + b^2 (12 + b^2) Log[1 + 4/b^2])

• Thanks for the answer. But can you please provide me the steps for the solution of the integration. – Parveen Bano Jun 28 at 6:50
• @ParveenBano you're on the wrong forum for that (this forum is about the Mathematica software). Maybe ask at the Mathematics StackExchange? – Roman Jun 28 at 6:56
• Thanks for the suggestion – Parveen Bano Jun 28 at 7:42