If your software does not have an automatic peak finder, you can use the NIST tool:

https://srdata.nist.gov/xps/EnergyTypeValSrch.aspx

In the case of your frame, that would match Rb3s:

https://srdata.nist.gov/xps/Spec_query.aspx?EType=PE&ENE=325.5&ENEERR=1.5&EType1=-1&ENE1=&ENEERR1=1.0&EType2=-1&ENE2=&ENEERR2=1.0&EType3=-1&ENE3=&ENEERR3=1.0

Do you also have other features that would match Rb? Otherwise, Zr would also be in the extended range of this energy.

Eventually a satellite peak? Such as a K-Beta excitation?

Depending on the conditions of your source, several ghost peaks could also come in mind. The best/easiest would be if you could upload your survey spectrum. And some information about your product would be helpful as well.

Rb 3s

Chem. Phys. 43, 117 (1979)

Check this reference

Sounds the approximate range for Mg Auger peaks - could be this

Likely an Auger peak of some description, or "ghost peaks" from contaminated sources