At first glance, adding of 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 in [1], that the quantum interference changes the situation impressively, so that the total partial wave l phase  of an electron scattered upon endohedral A@C_N is with good accuracy equal to the sum of scattering phases and of electrons upon atom A, stuffed inside the fullerene C_N. It means that a single atom contribution is quite large as compared to the background of C_N 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 the C_N. The inclusion of the latter proved to be very important since C_N 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 phases and cross-sections. Since the atom’s A phase is almost one-to-one reflected in , one has to investigate the effect of atom A polarization potential upon . Since 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 object 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 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 take 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. It appeared that 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 very deep Ramsauer-type minimum in the total elastic scattering cross-section. Surprisingly enough, it appeared that 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].        M. Ya. Amusia and L. V. Chernysheva, Pis’ma v ZhETF, 101, 7, 556-559, 2015, JETP Letters, 101, 7, 503-506, 2015.