Dipole bound anions, formed by electron addition to closed-shell neutral polar molecules, are unstable relative to autodetachment unless the dipole moment strength is sufficiently large. Long ago, Fermi and Teller demonstrated first that a point dipole can bind an electron in an infinite number of bound states, if its dipole strength exceeds Dc=0.6993 a.u. =1.625 D.

Subsequently, several authors found that this critical dipole strength was independent of the dipole length, also when the short-range repulsion of the core was taken into account. The consideration of rotational degrees of freedom in a real molecular system reduces the number of bound states to a finite number and increases the minimum dipole strength to support at least one bound state by 10 to 20 %, with respect to that of fixed dipole. In this case, Dc depends on the dipole length, the rotational state and the moments of inertia of the polar molecules.

Formation of a dipole bound anion has been difficult to observe experimentally for the very diffuse and loosely bound electrons are easily stripped away by thermal collisional processes and/or by the electric fields to which they are exposed in mass analyzers. Recall that the average distance between dipole bound electrons and their neutral polar molecules is typically 10-100 Angstroms.

However, recent experimental advances have made it possible to measure the energy of one dipole-bound electron very accuratly. It has even been possible to set up a technique that permits nondestructive separation of mass and geometrical distinct configurations of both neutral and charged polar weakly bound complexes, a problem of paramount importance for the study of the interactions of electrons with assemblies of solvent molecules in condensed phases.

Most of the attention devoted to dipole-bound anions has focused on singly charged species in a vacuum , and remarkably, the possibility of the existence of multiply charged anions or singly charged anions within an screening enviroment, in the field of an electric dipole has not been considered so far.

Given the importance of multiply charged anions and the relevance of screening effect exerted by the enviroment, in both physics and chemistry we have studied using variational calculations to minimize the expectation value of the Hamiltonian operator of one and, two mutually repelling electrons in the field of an electric dipole either in a vacuum within a screening enviroment.

Please refer to the Publications section or alternatively, drop us a note if you want to learn more about our research in this field.