Some chemists have also considered the 2-norbornyl cation to be best represented by the nortricyclonium ion, a C-symmetric protonated nortricyclene. This depiction was first invoked to partially explain results of a C isotope scrambling experiment. The molecular orbital representation of this structure involves an in-phase interaction between sp-hybridized orbitals from carbons 1, 2 and 6 and the 1s atomic orbital on a shared hydrogen atom (see Figure 5).