 mass calculated by: mass_true = mass*u +
mass excess +
elecrons*m_{e};
 v/c = sqrt{1.0  1.0/[(energy/mass_true+1)*(energy/mass_true+1)]}
 constant: c=29.9792458 cm/ns  speed of light
 constant: u=931.494013 MeV  atomic mass unit
 constant: m_{e}=0.510999890 MeV  electron mass
 Mass excess values are from the 2003 mass table of
G. Audi, A. H. Wapstra and C. Thibault,
Nuclear Physics A729 (2003) p. 337676.
This version of the Mass Table
was taken from NNDC at BNL;
