Nondipole photoelectron angular

In this equation, the spherical angles 6 and

defined relative to the photon momentum k, photoelectron momentum p, and photon polarization vector e, as indicated in Figure 1, fi i is a dipole photoelectron angular distribution parameter, yni and Sni are nondipole photoelectron angular distribution parameters. 

Figure 11 Nondipole photoelectron angular asymmetry parameter y A ( >) for Is photoionization of free Ne, Ne from neutral Ne Cgo as well as Ne from the fullerene anion Ne q0 (z < 0) [28], as indicated.

Figure 12 Ne Is nondipole photoelectron angular asymmetry parameter y A(a>) for the Ne C605 anion along with the dipole D and quadrupole Q amplitudes and cos A (A = 2 — ti) [28].

Figure 15 Calculated results [32] for a nondipole photoelectron angular-asymmetry parameter Ki aM for the Is photoionization of Ard>C6o, Ar Cgo C24o and Ar Cgo C24o C54o, as indicated, as well as of free Ar (dashed line).

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... 

Calculated results for the Ar nondipole Is photoelectron angular-asymmetry parameter yis(< ) for free Ar, Ar C60, Ar C60 (-240 and Ar C6o C240 C540 are shown in Figure 15 (the nondipole parameter Sns vanishes, by definition, and the dipole parameter fins = 2, i.e., is constant, nonrelativistically for the photoionization of ns-states). 

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