CC BY
14Complex Systems of Charged Particles and their Interactions with Electromagnetic Radiation 2016
MODIFICATION OF THE ELECTRON-ENDOHEDRAL SCATTERING CROSS-SECTION DUE TO INTERACTION BETWEEN FULLERENE
AND ATOMIC ELECTRONS
M.Ya. Amusia^**, L.V. Chernysheva**
*The Hebrew University, Jerusalem, Israel, e-mail: amusia@0l2.net.il **Ioffe Physical-Technical Institute, St. Petersburg, e-mail: Larissa.Chernysheva@,mail/ioffe.ru
At first glance, adding a single relatively small atom inside a fullerene should not affect the electron elastic scattering cross-section of the latter, since the presence of an additional atom inside alters inessentially the total size of the system under consideration. However, we have demonstrated recently [1], that the quantum interference changes the situation impressively, so that the total partial wave l phase Sf@CN of an electron scattered upon endohedral A@CN is with
good accuracy equal to the sum of scattering phases Sf and Sf" of electrons upon atom A,
stuffed inside the fullerene CN, and upon the fullerene itself. It means that a single atom contribution is quite large as compared to the background of CN cross-section.
In [1] we have performed calculations, assuming that the incoming electron feels the Hartree-Fock potential of the atom A as well as the static and polarization potential of CN. The inclusion of the latter proved to be very important since CN is a highly polarizable object, as compared to the atom A.
However, we know that the polarization potential of the atom A modifies essentially its scattering phases and respective cross-sections. Since the atom's A phase Sf is almost one-to-
one reflected in Sf@ Cn , one has to investigate the effect of atom A polarization potential upon
Sf@Cn . Because the fullerene is a highly polarizable object, it can affect the atom A polarization
potential leading instead to a potential that accounts it's modification by the fullerene's shell.
As concrete objects of calculations we choose almost ideally spherical fullerene C60 and endohedrals Ne@C60 and Ar@C60 with centrally located quite small and spherical atoms.
In our calculations, Ne and Ar are treated and polarization potential calculated in the random phase with approximation with exchange (RPAE) frame, while C60 is represented by a static square well potential, which parameters are chosen to represent the experimentally known electron affinity of and low- and medium energy photoionization cross-sections of C60. We
took into account also the polarization potential and developed an approximation that permits to calculate the polarization potential of an endohedral that includes effects of the fullerenes shell.
We found that a single added atom modifies considerably the elastic cross-section of electron scattering upon an endohedral. Starting already from 0.1 Ry of incoming electron energy, the destructive interference between C60 contribution and that of the inner atoms Ne or Ar, results in a deep Ramsauer-type minimum in the total elastic scattering cross-section. Surprisingly, the fullerenes electron shell modifies considerably the polarization potential of the stuffed inside C60 atoms Ne and Ar, so that this effect is quite visible in the total cross-section.
References
[1] Amusia, M.Ya., Chernysheva L.V., Pis'ma v ZhETF, 2015, 101, 7, 556-559
