Integrating Laguerre Polynomials - Fine structure hydrogen

sebhofer
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Hi

I have the following problem:
To calculate the fine structure energy corrections for the hydrogen atom, one has to calculate the expectation value for (R,R/r^m), where R is the solution of the radial part of the schroedinger equation (i.e. essentially associated laguerre polynomial) and m=1,2,3.
\int_{0}^{\infty} {dx} {(\mathrm{L}_n^k)}^2e^{-x}x^{k+1-m}
Solving the integral for n=1 is easy because the laguerre polynomials are normalised that way.
For m=2,3 it is much harder. I have already spent a few hours trying to get a solution by using the generating function of the laguerre polynomials, but no luck yet. Can anybody give me a hint how to do it?

Thx
Sebastian

Edit:
Can anybody tell me how to post latex in this forum pls. Sorry for my stupidity, but I just don't get it.
Edit 2: Thx for the help on latex Statuts X. Added integral to the post.
 
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There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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