A PERFORMANCE AND APPLICATIONS STUDY OF THE PHOTOELECTRON SPECTROMlCROSCOPE*

We review some recent work carried out in the area of Photoelectron Spectromicroscopy for both laboratory and synchrotron based instruments. This allows assessment of the technique’s capability for dealing with real world applications. In particular, a comparison of achieved performance is made with commercial laboratory equipment to illustrate the strength of the technique. Examples of applications are also given to highlight its versatility and flexibility. Finally we address some of the present limitations of the technique and make specific proposals to expand its applications role. . INTRODUCTION During the late 1970’s a new approach to conducting micro-area photoelectron imaging and spectroscopy was explored by an Oxford University group led by D. W. Turner (1, 2). The technique, dubbed Photoelectron Spectromicroscopy (PESM) uses a high field superconducting solenoid to guide and collimate electrons which are photo-excited from a sample situated close to the magnetic center of the system. The photoelectrons are then intercepted by some detector/spectrometer combination which is positioned on the solenoid axis (Figure 1). In general all of the photoelectrons are emitted with components of momentum both parallel and transverse to the magnetic field direction. The transverse momentum component has the effect of tightly binding each emitted electron to the magnetic field lines passing through the point of emission by virtue of the gyro-magnetic force. The parallel component translates the electron toward a region of decreasing field. Both components combine to produce a helical trajectory with its guiding center aligned with the magnetic field direction. As the electrons move into a region of decreasing magnetic field, the axial and radial Lorentz forces (see inset Figure 1) cause an interchange of the electron momentum from the radial to the axial sense (the process conserving both linear and angular momentum) until finally the electron motion becomes essentially linearized or collimated with the magnetic field direction. Stimitted to the Journal of Electron Spectroscopy and Related Phenomena. * Work Supported by the U.S. Department of Energy under Contract DE-ACO3-76SFOO515