Simplifying expressions

Questions
1

Hello guys,

I don’t know why but I’m having a problem to simplify my expression. I’ve already tried Simplify, FullSimplify and nothing. My expression is

(Exp[-Z*r/a]*Sqrt[Z^3/a^3])/(Sqrt[Pi])

what I really want is to put these two squares together: Sqrt[Z^3/a^3]/Sqrt[Pi]

Thanks for the attention!

2

How about

In[5]:= PowerExpand[Sqrt[Z^3/a^3]/Sqrt[Pi]]

Out[5]= Z^(3/2)/(a^(3/2) Sqrt[\[Pi]])
3

Mathematica insists to turn Sqrt[a/Pi] into Sqrt[a]/Sqrt[Pi], because Pi is larger than zero.
Yon can inactivate Sqrt to bypass the automatic rules:

Sqrt[Z^3/a^3]/Sqrt[Pi] /. Sqrt[x_]/Sqrt[y_] :> Inactive[Sqrt][x/y]