Table 1. Niobium 3d5/2 binding energy values from NIST database[1].
Niobium metal spectrum taken here gave a binding energy value 202.3 eV. It is fit with an asymmetric peak shape defined as A(0.38,0.6,10)GL(10) or LA(1.2,5,12). Doublet separation is 2.72 eV.
References:
1) http:/srdata.nist.gov/xps/
