Mott scattering/detector

Spin analysis was carried out by a Mott-scattering detector with a spherically symmetric acceleration field operated at typically 70 keV without retarding potentials [3]. Surface barrier detectors were used as electron detectors. The figure of merit x ///q amounts to about 2.4 x 10 ". The advantages of this type of... 

In these relations the interest lies in the spin-polarization vector of the photoelectron itself, i.e., the detector response Q is assumed to be always perfect, Qt= +1. The same procedure applies if the response of an actual detector with Q, < 1 to polarized electrons is calculated (see below where, for the case of Mott scattering, Q, has to be identified with the Sherman function Ss). 

The first prerequisite for measurement of photoelectron spin-polarization is the ability to separately detect the photoelectrons ejected from the different fine-structure levels (e.g., 2n3/2 and 2n1/2 for HX+ X2n). When the molecule contains a heavy atom (e.g., large spin-orbit splitting), it becomes easier to use the electron kinetic energy to distinguish the photoelectrons ejected from the different fine structure channels. For spin-polarization analysis, the accelerated electron beam (20-120 keV) can be scattered by a thin gold foil in a Mott-detector. The spin-polarization is determined from the left-right (or up-down) asymmetry in the intensities of the scattered electrons (Heinzmann, 1978). Spin polarization experiments, however, are difficult because the differential spin-up/spin-down flux of photoelectrons is typically one thousandth that obtained when recording a total photoionization spectrum. 

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