Doubly-charged Negative Ion of C60 Molecule

Abstract

Within the Dirac- and Lorentz-bubble potential models an electronic structure of the doubly-charged negative ion \(C_{60}^{2-}\) has been studied by a variational method. It is shown that even in the first approximation of this method when a trial wave function of the two electrons is represented as a product of one-electron functions the total energy of the system is negative, a manifestation of the existence of a stable state of the doubly-charged negative ion in these models. The second electron affinity of C60 according to estimation is about \(\epsilon\)2 \(\approx\) 1 eV. The photodetachment cross sections \(\sigma\)(\(\omega\)) of this ion have been calculated as well. Near threshold \(\sigma\)(\(\omega\)) is found to exhibit peculiar and interesting behavior. The first cross section accompanied by the transformation of the doubly-charged negative ion into a singly-charged one is exponentially small near the process threshold. The second cross section corresponds to the photodetachment of a singly-charged ion; it increases at the threshold as a power function of the kinetic energy of the photoelectron. These cross sections are of the same order as the photodetachment cross sections of atomic ions with the same electron affinity.