Table 3 The heteroatom site-selectivity of selenophene, thiophene and furan at various photon energies, as determined by the Se 3d, S 2p and O 1s orbital cross sections (\(\sigma _{\text {X}\,{nl}}\), where X is the heteroatom, n is the energy level, and l is the orbital type), and by the total heteroatom cross sections (\(\sigma _{\text {X}}\), including all accessible atomic orbitals of the heteroatom at the given photon energy)⁴⁴. The preference for site-selective ionization is expressed as a fraction of the value expected for the whole molecule (\(\Sigma \sigma _{\text {C}_4\text {H}_4\text {X}}\), where the sum represents the accessible atomic orbitals of the constituent atoms at the given photon energy).

From: The inner-shell ionization and fragmentation of selenophene at 120 eV