Dear Tammana,

I don't know the exact number. But you can check this from  NIST XPS database from the internet. From here, you will find the value in accordance with the oxidation state of Ce in CeB6. 

Good luck!

Thank u Dr Ehsan for your response to my question. But unfortunately I could not get the data for CeB6. 

Dear Sir,

for CeB6, you can find a Ce-3d spectrum (probed with Mg-Ka excitation) in Fig. 3 in  J. Phys. Soc. Jpn. 64 pp. 302-307 (1995).

Sincerely, FM

Be careful with photoemission spectra of Ce, because it can contain also shake-up satellites. For example, see below:

https://www.researchgate.net/publication/256351183_Rare-earth_sesquisulphides_investigation_by_ELS_and_XPS

https://www.researchgate.net/publication/222346747_XPS_study_of_ceramic_three-way_catalysts

Article Rare-Earth Sesquisulphides Investigation by ELS and XPS

Article XPS study of ceramic three-way catalysts