FIAS Scientific Report 2011 - Frankfurt Institute for Advanced Studies ...

Photo-processes in fullerenes and endohedral systems
Collaborators: A.V. Solov’yov 1 , A.V. Korol 1 , A.V. Verkhovtsev 1 , R.G. Polozkov 2 , V.K. Ivanov 2 , J.-P.
Connerade 3 , A. Müller 4
1 Frankfurt Institute for Advanced Studies, 2 St. Petersburg State Polytechnic University, Russia, 3 Imperial College,
London, UK, 4 Justus-Liebig-Universität Giessen, Germany
Short description:
Within this project we study photo-processes (photoabsorption, bremsstrahlung, light scattering) in pristine and
endohedral fullerenes. Special attention is paid to the influence of the fullerene on the encaged atom (molecule).
Main results:
We demonstrated, that the Auger decay rate in an endohedral atom is very sensitive to its location in the
fullerene cage. Two additional decay channels appear in an endohedral system: (a) the one due to the change in
the electric field at the atom caused by dynamic polarization of the fullerene electron shell by the Coulomb field
of the vacancy, (b) the channel within which the released energy is transferred to the fullerene electron via the
Coulomb interaction. The relative magnitudes of the correction terms are dependent not only on the position
of the doped atom but also on the transition energy. Additional enhancement of the decay rate appears for
transitions whose energies are in the vicinity of the fullerene surface plasmons energies of high multipolarity.
It is demonstrated that in many cases the additional channels can dominate over the direct Auger decay resulting
in pronounced broadening of the atomic emission lines.
The case study, carried out for Sc 2+ @C80 (see Fig. 1), shows that narrow autoionizing resonances in an isolated
Sc 2+ are dramatically broadened if the ion is located strongly off-the-center. Using the developed model we
carried out quantitative analysis of the photoionization spectrum for the endohedral complex Sc3N@C80 and
demonstrate that the additional channels are partly responsible for the strong modification of the photoionization
spectrum profile detected experimentally by Müller et al., J. Phys.: Conf. Ser. 88, 012038 (2007) (see Fig. 2).
Figure 3: The structure of the
Sc3N@C80 complex.
Related publications in 2011:
Photoionization cross section (Mb)
60
40
20
0
+
Sc N@C 3 80
35
exp. (Mueller et al., 2007)
theory (Korol & Solov’yov, 2010)
40
Photon energy (eV)
45
Figure 2: Photoionization of Sc3N@C80: Experiment
(Müller et al., 2007) vs theory [1].
1. A.V. Korol, A.V. Solov’yov, Vacancy decay in endohedral atoms: The role of an atom’s non-central
position, J. Phys. B: At., Mol., Opt. Phys. 45, 085001 (1-17) (2011).
99