The following calculates elastic scattering kinematics.
a + b -> c + d, where c = a and d = b .
m(electron) = 0.511 MeV
Some useful atomic masses (MeV).
m(1H)=938.783, m(2H)=1876.124, m(3H)=2809.432
m(3He) = 2809.413, m(4He) = 3728.40