ESCA and XES/XAS difference?

[makeendsmeet]

Hi,

Both ESCA and XES/XAS can measure HOMO and LUMO. However, I don't understand the difference between the two methods. Also, which method is more accurate? Thanks.

[Modey3]

ESCA or XPS involves measuring the kinetic energy of a photoelectron. XES or EDS involves measuring the characteristic radiation from an atom, which results from the relaxation of an atom with a hole in a core shell. The main difference between XES and EDS is that in XES the atom isn't ionized (the electron is just excited to a higher energy level) and in EDS the atom is ionized. I would say the the best way of measuring the HOMO/LUMO levels to use ESCA since the measured electron kinetic energy corresponds directly with the binding energy of the occupied state.

modey3