First Isotope Second Isotope
Isotopomer Frequency/10M Mass   Isotopomer Frequency/10M Mass Isoptomer Frequency/10M Mass
15N       15N15N     33S17O    
Negative Ion Data?
33S       34S     18O    
FALSE 13C       33S15N     33SD    
17O       37Cl     13C13C    
D       81Br     13C17O    
          33S33S     17O17O    
        13C15N     13CD    
Protonated Mass   15N17O     17OD    
        13C33S     DD    
Isotope Ratio     15ND          
1) Berglund and Wieser, "Isotopic Compositions of the Elements 2009" Pure and Applied Chemistry Vol 83 No 2 pp 397-410, 2011.                                                   
2) Meija et. al. "Atomic weights of the elements 2013 " Pure and Applied Chemistry Vol 88 No 3 pp 265-292, March 2016.