Confinement and correlation effects in the Xe@C60 generalized oscillator strengths

The impact of both confinement and electron correlation on generalized oscillator strengths (GOS's) of endohedral atoms, A@C-60, is theoretically studied choosing the Xe@C-60 4d, 5s, and 5p fast electron impact ionization as the case study. Calculations are performed in the transferred to the atom energy region beyond the 4d threshold, omega = 75-175 eV. The calculation methodology combines the plane-wave Born approximation, Hartree-Fock approximation, and random-phase approximation with exchange in the presence of the C-60 confinement. The confinement is modeled by a spherical delta-function-like potential as well as by a square well potential to evaluate the effect of the finite thickness of the C-60 cage on the Xe@C-60 GOS's. Dramatic distortion of the 4d, 5p, and 5s GOS's by the confinement is demonstrated, compared to the free atom. Considerable contributions of multipolar transitions beyond dipole transitions in the calculated GOS's are revealed, in some instances. The vitality of accounting for electron correlation in calculation of the Xe@C-60 5s and 5p GOS's is shown.