About the hyperfine energy splitting of a positronium

[S_klogW]

I have read from DJ Griffiths Quantum Mechanics that the electron-positron annihilation process will enlarge the hyperfine splitting of the positronium ground state. More precisely, the actual splitting is larger than that we calculated only considering the spin interaction between the positron and the electron in the same way as we did for the hydrogen atom.
Does anyone know how to get an intuitive physical point of view about this? I am a sophomore undergraduate so I can not calculate it using Quantum Electrodynamics now.

Thanks

 

[andrien]

electron and positron can annihilate in positronium which is not the case in hydrogen atom.this one photon virtual annihilation process(triplet state) gives rise to a matrix element from which the contribution to hyperfine splitting can be calculated using it's non relativistic form and Fourier transform of the matrix element.