⁴⁰Ar-Argon

 
40Ar has 18 protons and 22 neutrons.
40Ar is a stable isotope.
The mass excess of 40Ar is -35039.89997 with an uncertainty of ±0.00218.


The mass was measured using a Penning Trap and the related equations include:

Influence				 Equations

       44.7%		  	    C3H4-40Ar  1  
		       34.2%			   C2D8-40Ar 1  		  
      14.1%			   20Ne2-40Ar 1  










Reference

1. F. DiFilippo, V. Natarajan, M. Bradley, F. Palmer, D.E. Pritchard (1995)Accurate atomic mass measurements from Penning trap mass comparisons of individual ions
 Physica Scripta  1995(T59)
https://iopscience.iop.org/article/10.1088/0031-8949/1995/T59/018