Photoionization of C4 molecular beam: Ab initio calculations
Résumé
Large computations are performed on the C cation in order to characterize its stable isomers and its lowest electronic excited states using configuration interaction methods and large basis sets. Several stable isomers are found including a linear C(l-C), a rhombic C(r-C) (or cyclic), and a branched (d-C) structure. Our calculations show a high density of electronic states for all of these isomers favoring their interactions. By combining the present ab initio data and those on neutral C4, the l-C4()+hl-C(+)+e−, d-C4()+hd-C(+)+e−, and r-C4()+hr-C(+)+e− vertical photoionization transition energies are computed at 10.87, 10.92, and 10.77 eV, respectively. Photoionizing a C4 molecular beam results on an onset at 10.4–10.5 eV and then to a linear increase of the signal due to the opening of several ionization channels involving most of the C4 and C isomers and electronic states.