Auger decay parameters α₂for krypton M_4.5-N_2.3N_2.3transitions

Abstract

The Auger electron decay parameters u2 for krypton M4,,-N2,,N2,, transitions induced by photon impact are determined experimentally and compared with theoretical predictions. Apart from the M4,5-N2,3N2,3 ' S o transitions, poor agreement is found, which might be attributed to the angular momentum coupling scheme used in the theoretical approach.Inner-shell ionisation followed by an Auger transition is described normally as a two-step process. As a consequence, the angular distribution parameter, p k , of the Auger electrons emitted can be factorised into two constituents: the alignment tensor component, d k o (later referred to as the alignment parameter), and the Auger decay parameter, a,. d k o describes the differences in the population probabilities of the magnetic sublevels of the intermediate inner-shell hole state while the decay parameter, f f k , depends on the contributing Auger amplitudes Kabachnik 1977, Aberg andHowat 1982). If the decaying ion state is produced by photoionisation, dipole selection rules restrict the possible k values to k = 2 (and trivially k = 0 ) , and the anisotropic angular distribution of Auger electrons is given by: I ( @ ) = Io( 1 + P,P,(COS 0))(1) with p2= OP2,,a2 and 0 the angle between the Auger electron and the electric vector of the linearly polarised incident radiation.Here, we will concentrate on the P2 values caused by photoionisation. Contrary to the angular distribution parameter, P 2 , of photoelectrons, the Auger electron angular distribution parameter, p2, is usually small and restricted within a much more limited range than between -1 and 2. This makes the experimental determination of p 2 and

XPS Measurement of YBa2Cu3Oy Compounds Heated at Various Temperatures

“…The experimental set-up and the measurement technique has been described in detail elsewhere [30,34], so that only a brief description of the experiment is given below. Linearly polarized monochromatized synchrotron radiation from the crossedundulator beamline U2-FSGM at BESSY I, Berlin, with an energy of ω = 65.110 eV was used for the excitation of the 4d 9 5/2 5p 6 6p 3/2 (J = 1) resonance in gaseous Xe. Fluorescence (step 3) intensities have been measured in directions parallel, I (0 • ), and perpendicular, I (90 • ), to the electric vector of the incoming radiation and perpendicular to the propagation direction of the incoming radiation.…”

“…The AOs for the ε j -electrons in the continuum are needed to compute the phase shift in equation (4) and matrix elements of the Coulomb operator in equations (4) and (9). These AOs were obtained in the frozen core of the configuration 5p 4 6p by solving the PF equation [41,42].…”

“…Studying the angular distribution of the electrons emitted in step 2 of process (1) can provide information about the alignment of the 5p 4 6p levels only in some specific cases, whereas the measurement of β fl by PIFS provides this information for all 5p 4 6p levels. Indeed, equation (4) describing the angular distribution of Auger electrons contains the coherent summation over the partial channels which can be reduced to the incoherent summation determining A 20 , equation (9), only in those cases when only one strongly dominating decay channel exists in the sum (4). In contrast, the angular distribution of fluorescence radiation is directly dependent on the alignment of the initial level of the fluorescence so that A 20 (E 1 J 1 , ω) of the respective ionic levels can be determined directly from the angular resolved PIFS measurement.…”

“…The A 20 values of the 5p 4 6p levels were calculated in the stepwise scheme (1) using equations (9) and (10) …”

“…Further theoretical investigations of the influence of different approximations in the computation of atomic orbitals involved in the calculation of β Aug and of many-electron effects have been carried out for the Auger effect in Ar [7], Kr and Xe [7,8]. The measurement of β Aug performed in [9] for the Kr atom confirmed, to a large extent, the theoretical prediction [5]. The efforts connected with studying the angular distributions of Auger electrons increased after the resonance Auger spectra for Xe [10,12], Kr [11] and Ar [13] were obtained, which occur when an inner electron is photoexcited to a resonance state, not to the continuum.…”