I am trying to learn the Photoelectron velocity map imaging. While I was going through the article "Chem. Soc. Rev., 2009,38,2169-2177", it is said that the "photoelectron spectrum reflects the energy eigenvalues of the parent atomic or molecular system, while the phtoelectron angular distributions reveal the characteristics of the corresponding wave functions" (in the page 2170 of the said reference). I didn't understand what it is mean by the statement "photoelectron angular distributions reveal the characteristics of the corresponding wave function"!. Can anybody please explain me this?
You know how the shape of atomic orbitals (s, p, d) depends on the angular momentum of the electron. This momentum can be preserved in photoelectrons, and from the shape of the electronic cloud hitting the detector you can determine not only the energy, but also the angular momentum of the electron. It gets more complicated for many-electron atoms and molecules, but the basic idea is the same.