There are plenty of websites that deal with XPS. Some address the technique as such, others present refence data.
NIST X-ray Photoelectron Spectroscopy Database (srdata.nist.gov)
XPS Table Of Elements (thermofisher.com)
X-Ray Properties of the Elements (henke.lbl.gov)
X-Ray Properties of the Elements (xdb.lbl.gov)
XPS: Xray Photoelectron Spectroscopy (lasurface.com)
XPS - Science topic (www.researchgate.net)
X-ray Photoelectron Spectroscopy (XPS) Reference Pages (www.xpsfitting.com)
Surface chemical analysis — Vocabulary — Part 1: General terms and terms used in spectroscopy (www.iso.org)