Photoelectic cross-section question

[jsc314159]

Homework Statement

Show that if we consider photoemission from the 1s state of a charge Z atom,
<br /> \sigma \propto Z^5}} <br />, in the limit p_fa_0/Z\hbar &gt;&gt; 1.<br />

Homework Equations

<br /> \sigma = \frac{128a_0^3\pi e^2p_f^3}{3m\hbar^3\omegac[1+p_f^2a_0^2/\hbar^2]^4}} <br />

The Attempt at a Solution

Actually I know how to do this. a_0 -&gt; a_0/Z. My question is why is this so? What is the physical interpretation/what does it mean?

jsc

 

[jsc314159]

I think the reason a_0 -&gt; a_0/Z is because the Coulomb potential in the Hamiltonian changes from q^2/r to Zq^2/r. Is that right?

jsc