Speaker
Byron Smith
(University of Tennessee)
Description
The interaction of an electron with an anion is characterized by a long-range coulomb repulsion and a short range polarizability attraction giving rise to a coulomb barrier. The permanent addition of an extra electron to a negatively charged anion requires tunneling through the barrier or attachment of the electron over the top of this coulomb barrier followed by disposal of the excess energy. Charge-exchange collisions of an anion with an alkali atom utilize the latter channel to produce permanent dianions with cross sections of ~ 1 Angstrom^2. We have previously examined the reaction TCNQ-F_4^- + Xe -> TCNQ-F_4^{--} + Xe^+ and reported a delayed threshold and quantum phase interference effects in the charge exchange cross section. [1] Employing sodium as the collision partner, the cross section is seen to increase with decreasing energy with a threshold below 180 eV (com). A new apparatus has been constructed to allow measurements down to energies below the expected threshold (~ 41 eV, laboratory energy based upon a 1 eV second electron affinity). This method has been used to study the reaction TCNQ^- + NA -> TCNQ^{--} + Na^+ and will provide one of the first measurements of second electron affinities for molecular anions. [1] S. Yu. Ovchinnikov, et al. Phys. Rev. A, 73, 64704(2006).
