Spin polarization of Auger- and of photoelectrons from barium atoms exposed to circularly polarized radiation and their cross comparison

Abstract

Abstract.New results of spin polarization of both photoelectrons and Auger electrons are reported after 5p photoionization of free Ba atoms with circularly polarized light. A substantial polarization transfer from the spin polarized photons to the spin polarized photoelectrons and via the hole state orientation to the spin polarized Auger-electrons is observed. The cross comparison of the results for photoelectrons and Auger-electrons allows a quantitative test of the assumed two step model where both electron-emission processes occur in sequence. 32.80.Hd Creation of vacancies in inner atomic shells by photon or particle impact often gives rise to subsequent Auger decay. Recently, these Auger electrons have been measured to be strongly spin polarized for the electron spectroscopy studies with free barium atoms [1] and Rb-adsorbates [2], where the primary photoemission process has been performed by means of spin polarized i.e. circularly polarized radiation. In their emission characteristics these Auger electrons reflect a non-statistical population of the magnetic substates of the intermediate ionic state produced by the spin oriented initial impact [3,4]. Consequently, an orientation of the intermediate state can be transferred partially to the Auger electron spin polarization [5,6]. On the other hand the data of spinand angle resolved Auger spectroscopy can be used to determine alignment and orientation of the intermediate photoion state from the experiment [ 1 ]. Cross comparison of these results with the corresponding dynamical parameters characterizing the primary photoelectron emission process, angular distribution and spin polarization parameters which form a "complete experiment", should answer whether photoelectron and Auger electron emission are subsequent processes in a two-step model or whether they have to be seen as a dynamical combi-

Angle and spin resolved Auger and photoelectron spectroscopy on Rb-layers by means of circularly polarized VUV radiation

“…In agreement with the corresponding photoionization and Auger process of free Ba atoms [14] (also with two outermost s electrons in singlet state configuration) the Auger emission from the Rb adlayer atoms can be quantitatively described within the non-relativistic LS approximation while the photoemission deviates from this model due to non vanishing differences in the dipole matrix elements cd . It is worth noting that the relationships of the non-relativistic approximation [11] A3=2 -½A½ and a~ = -½~± are not fulfilled.…”

“…It is worth noting that the relationships of the non-relativistic approximation [11] A3=2 -½A½ and a~ = -½~± are not fulfilled. 7 From t~he dynamical parameters for photoemission given above, the Auger electron spin polarization can be calculated within an atomic model using the non-relativistic LS-approximation (neglecting any influence of the spin-orbit interaction in the continuum states) [14]. Thereby the two step model [15] is applied, treating the emission processes of photoelectrons and Auger electrons as independent and subsequent processes.…”