Ion source effect on the bond length of 4 HeH +

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±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.