To understand the anti-resonances of butane, QI maps are used to analyze the electronic transmission, as shown in Figure . Specifically, the QI maps for the cases with dihedral angles of 0 • and 180 • are presented at three different energies: E F (with E = 0eV) and the energies of the two antiresonances for 0 • (E = ±2.23eV). In our model, the σ-system of butane has 6 σ orbitals, the QI map is a 6 × 6 block matrix.