Angular asymmetry

The latter equation assumes a 100% linearly polarized ionizing radiation, a is the fine structure constant, Nni is the number of electrons in a nl subshell, Dni->ei l is a radial dipole photoionization amplitude, fini is the dipole photoelectron angular asymmetry parameter, and A i2 is the electric dipole-quadrupole interference term arising due to the correction term ikr in the above expression for Mab,... 

As an illustration, calculated data [36] for the Ne Is, 2s and 2p photoelectron angular asymmetry parameters from Ne C60, both in the 5- and A-potential models, are depicted in Figures 6-8. Note, the dipole parameter /3ns = 2,... 

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].

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). 

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).

Nonrelativistically, the dipole ns photoelectron angular asymmetry parameter /9 s( >) is independent of the photon energy or, = 2. This is because,... 

Similarly to the angular asymmetry parameter, / , the spin-polarization parameters have signed values and their expressions, as function of contributing transition moments, in principle permit determination of the relative signs of these transition moments. However, in contrast to the situation for atoms, the number of relevant unknown parameters exceeds the number of experimentally measurable quantities. Nevertheless, measurement of both resonance widths and spin-polarization parameters can considerably narrow the assignment possibilities. This is particularly true in the region between the two ion-core fine-structure thresholds, for example, 2n3/2 and 2n1/2 of an AB+ 2n state. 

Recall Eq. (8.11.9), which specifies that the angular asymmetry parameter, / , does not exhibit this opposite sign behavior,... 

The parameter [Equation (18)] is used to take into account deviations from 0 conditions (23). This approach has been evaluated with good success using polystyrene samples (21,24). If a viscosity detector is used in series with a right-angle light-scattering detector. Equation (16) can be used in an iterative procedure to correct for angular asymmetry (see p. 116). 

The angular asymmetry factor, accounting for anisotropy of the photoelectron emission, depends on the angle 7 between the X-ray beam and the direction of photoelectron collection (Fig. 16b). 

Obviously, the way of considering the transmission function must be consistent with that used to treat experimental data. Here the influence of the photoemission anisotropy parameter (L) is dropped, which is strictly correct when s peaks are used or y is close to the magic angle (cf. the section on Angular Asymmetry Factor). 

The closeness between IMFP and AL is illustrated by computations performed with the NIST database. Furthermore, the difference between using IMFP and AL for computing intensities is reduced by the fact that photoelectrons are emitted in all directions in the soM. It should vanish when the angular asymmetry factor L is equal to 1, i.e. with spectrometers in which 7 is close to 54.7°. 

Notation used for 2s and 2p subshells in Auger spectroscopy Average angular asymmetry factor Nonprotonated nitrogen Protonated nitrogen... 

Factor used to calculate the angular asymmetry factor L Angle between the direction of incident X-rays and the normal to the sample-holder plane... 

The angular asymmetry parameter /-a(y) describes how the intensity of a particular type of core-level line varies with the angle y between the incoming x-rays and the outgoing photoelectrons. 

Fig, 13. Angular asymmetry parameter 3 for the 2s subshell of carbon. The final state thresholds are ... 

A is the measured differential hfs anomaly, determination is that it provides a new operator ent from the magnetic moment (] = g + gjW, with which to test nuclear wave functions. The square Bracket is a tensor product of order 1 between the spin operator and the spherical harmonic Y. It is a measure of the angular asymmetry of the nuclear spin distribution. 

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