The effect 5B, of the Coulomb interaction on the A separation energy Bz of~He was obtained by variational calculations made for~He and 'He. These calculations were made for several values of q in the range 0&q &9 where qe is the proton charge, i.e. , the Coulomb repulsion was artificially boosted. For q &3, the dependence on q is linear, and interpolation to q =1 gives the physical values with improved accuracy: -AB, =0.05+0.02 and 0.025+0.015 MeV for the ground and excited state, respectively. This procedure also gives more accurate values for the differences between the proton and neutron radii of He. The corresponding differences of B~between~He and~H, to be attributed to charge symmetry breaking effects, are then 0.40+0.06 and 0.27+0.06 MeV. From these values we obtain a phenomenological charge symmetry breaking potential which is effectively spin independent.An examination of meson-exchange charge symmetry breaking models shows that these are consistent with the phenomenological charge symmetry breaking potential for the triplet but not for the singlet case.

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