Ion source effect on the bond length of ⁴HeH⁺

The bond length of ⁴HeH⁺ resulting from collision-induced destruction is measured at 1.4420 MeV using the Coulomb Explosion Technique. The measured bond length of ⁴HeH⁺ is 0.094\pm 0.003nm. The bond length of ⁴HeH⁺ obtained with our radio frequency (RF) ion source is larger than that obtained with a duoplasmatron ion source at Argonne National Laboratory (ANL), but the bond lengths of H₂⁺ and H₃⁺ obtained separately by ANL and by us with the two different ion sources are consistent with each other, which implies that there exists an ion source effect on the bond length of ⁴HeH⁺. The main reason why the ⁴HeH⁺ bond lengths obtained by the two different ion sources are different is also discussed.