We describe recent experimental triple-differential cross sections of ionization by the impact of both protons and positrons by means of a single, kinematically exact theory. This model incorporates all the interactions in the final state on an equal footing and keeps an exact account of the three-body kinematics. We show that these provisions make it possible to evaluate any multiple-differential cross section for any given mass configuration, and analyse how it changes with the relative masses of the three particles in the final state. We analyse the differences in the electron cusp formation by both heavy and light projectile impact at the double-differential cross section level.

Electron double and triple differential cross sections are calculated as a function of projectile momentum transfer for ionization of ground and excited state hydrogen by 3.6 MeV u-1 C6+ and Au53+ ions. These three-body Coulomb systems are investigated using the classical-trajectory Monte Carlo and continuum distorted wave methods that incorporate all interactions including the nuclear-nuclear potential. The calculations allow one to distinguish cross section features associated with three collision mechanisms. The first is due to distance collisions that lead primarily to a binary interaction between the projectile and electron. The second is a strong three-body interaction by the projectile with both the electron and the target ion when the projectile passes between the electron and its parent nucleus. These two mechanisms result in binary peak electrons located near the momentum transfer vector Q with active participation by the recoil ion along -Q in order to determine the overall momentum transfer magnitude. The third mechanism, which is present only for fast highly charged ion impact, yields electron spectra that here-to-fore have not been observed. Rather than the electrons being scattered near the angle θ associated with the momentum transfer vector Q, they are found at an angle of 360°-θ. Such electrons are due to a close collision of the projectile with the target nucleus with the electron being forced to swing by its parent. These electrons are not so-called recoil electrons associated with the angle 180° + θ. Moreover, in this case neither the recoil ion nor the electron spectra peak near Q. Calculations are also presented for collisions with excited hydrogen in order to assess the collision dynamics as a function of the radial dimensions of the target atom.

In this manuscript we report a high-level ab initio study of anion-pi interactions involving N9-methyl-adenine, N6-methyl-adenine, N9-methyl-hypoxanthine, a dimer of N9-methyl-adenine, and N9,N9'-trimethylene-bisadenine. DNA bases like adenine are electron-deficient arenes that are well suited for interacting favorably with anions. We demonstrate that these compounds are able to interact favorably with anions. N9-Methyl-adenine, N6-methyl-adenine, and the dimer of N9-methyl-adenine interact with the anion via the six-membered ring more strongly than adenine due to cooperativity effects between the noncovalent pi-pi and anion-pi interactions. This pattern, i.e., coexistence of pi-pi and anion-pi bonding, is observed experimentally in the solid state. Finally, we report the solid-state characterization of two new compounds N6,N6'-dimethylene-bisadenine hydrochloride and an outer-sphere complex of protonated N9,N9'-trimethylene-bishypoxanthine with zinc tetrachloride anion, that exhibit interesting anion-pi interactions. They are in strong agreement with high-level theoretical calculations.