Photoionization of encaged atoms

In summary, despite the assumption of a zero thickness A of the fullerene cage [38,39] being an obvious drawback of the quantum mechanical model, this model seems to be more realistic than the discussed classical models of the C cage [43,44], Correspondingly, in the present paper, the screening factor F(co) from [38,39] is used whenever the dynamical-cage approximation is deemed to be appropriate for the calculation of the photoionization of the atom encaged in Cm-... 

This model was, perhaps, first suggested by Pushka and Nieminen [16] in conjunction with the jellium model of C60- Later on, it was used, independently, in another work [47], At a later stage, the idea was greatly extended to numerous studies of various aspects of structure and photoionization of atoms A encaged in various spherical fullerenes [15,20— 22,27-33,42-44]. 

An alternative simple modeling of doped fullerenes, specifically, A C6o, was developed initially in [34]. It was then used extensively in a number of photoionization studies of thus encaged atoms [34 41], The method is based on approximating the C60 cage by a spherical potential V(r) which differs from zero only within an infinitesimally thin wall of a sphere of radius RC/ the latter being considered the C60 radius, Rc = 6.639 au [47] ... 

The thus determined wavefunctions of the continuous spectrum of the atom A encage in C60, combined with the wavefunctions of the ground state of the free atom A, are used in determining the total and differential photoionization cross sections of the encaged form. 

In the framework of the A-potential model, combined with the frozen-cage approximation, the problem is solved simply. Namely, HF wavefunctions and energies of the encaged atom, solutions of the extended to encaged atoms Hartree-Fock equations (2), must be substituted into corresponding formulae for the photoionization of an nl subshell of the free atom, Equations (18)-(26), thereby turning them into formulae for the encaged atom (to be marked with superscript " A") rrni(o>) —> a A(co), Pni(fi>) Yni o>) - and 8ni((o) - 8 A(co). This accounts... 

Thus, F(oj) has a complicated codependence. The latter will be mirrored in the photoionization cross section of the encaged atom. Correspondingly, the photoionization cross section of the encaged atom in the dynamical-cage approximation might differ greatly from that in the frozen-core approximation, both quantitatively and qualitatively. 

The discovery of confinement resonances in the photoelectron angular distribution parameters from encaged atoms may shed light [36] on the origin of anomalously high values of the nondipole asymmetry parameters observed in diatomic molecules [62]. Following [36], consider photoionization of an inner subshell of the atom A in a diatomic molecule AB in the gas phase, i.e., with random orientation of the molecular axis relative to the polarization vector of the radiation. The atom B remains neutral in this process and is arbitrarily located on the sphere with its center at the nucleus of the atom A with radius equal to the interatomic distance in this molecule. To the lowest order, the effect of the atom B on the photoionization parameters can be approximated by the introduction of a spherically symmetric potential that represents the atom B smeared over... 

---