LAUSR

Abstract The kinetic energy of ions produced by a Coulomb explosion, in which multiply charged molecular cations dissociate, is determined by the charge number, mass, and geometric configuration of the ions upon explosion. Although the importance of the structural deformation and migration of atoms on kinetic energy variations is well known, there has been little investigation into the effect of charge localization before the ions are released. In this study, the angular distributions of iodine and carbon ions ejected from linear alkanes, which have one iodine atom on each side of an alkyl chain having one to six carbon atoms, are measured. The highly charged iodine ions (I4+, I5+) are emitted mostly along the laser polarization direction, whereas the angular distribution of iodine ions becomes isotropic the longer the alkyl chain and the lower the charge number of iodines are. Furthermore, the longer the alkyl chain, the higher the kinetic energy of iodine and carbon ions. The emission of ions is discussed in terms of the selective ionization of aligned molecules based on their molecular orbitals. The charge localization during ionization in strong alternating electric fields followed by two-body Coulomb explosion via a C I bond cleavage is proposed.