Relativistic and Quantum Electrodynamics Effects in the Helium Pair Potential

The helium pair potential was computed including relativistic and quantum electrodynamics contributions as well as improved accuracy adiabatic ones. Accurate asymptotic expansions were used for large distances R. Error estimates show that the present potential is more accurate than any published to date. The computed dissociation energy and the average R for the He-4(2) bound state are 1.62 +/- 0.03 mK and 47.1 +/- 0.5 angstrom. These values can be compared with the measured ones: 1.1(-0.2)(+0.3) mK and 52 +/- 4 angstrom [R.E. Grisenti et al., Phys. Rev. Lett. 85, 2284 (2000)].