Subject: XPS of Perfluoropolyether (PFPE) oil

From: [email-masked] (Pat Hogue 1-2183)
Date: Tue, 16 Nov 93 13:11:11 MST

Dear Netters, I need help with a thesis related question.

     An XPS sprectrum was obtained on PFPE oil (Bray 815Z) 
as a film on aluminum foil.  Three peaks appeared at low
 binding energies: 10.69 ev, 16.59 ev and 20.56 ev.  
The spectroscopist refers to these peaks as "valence level
 density of States".  The higher energy O, F and C peaks 
appeared normal.

     My simple AM1 model PFPE gives a HOMO energy of -13.4 ev 
which, according to Koopmans' theorem is about equivalent to 
the ionization potential.  I would like to use the XPS data as 
evidence that my model is a good representation of reality but
the 2.7 ev difference begs for an answer.

     My answer is that the work function of a specimen is often 
2 to 4 ev lower than its (gas phase) ionization potential due to
image forces.

     Conclusion: the XPS data supports the model.  Comments
 are more than welcomed.

Pat Hogue