Analyzer system capable of determining energy and direction of charged particles in ultrahigh vacuum

We have constructed and tested a system capable of measuring the energy of charged particles emitted from a sample at any angle relative to the sample or the incident beam of exciting particles. The energy analysis is accomplished by a 180 degrees spherical deflecting-type analyzer, operated at constant pass energy with a series of electrostatic lenses. The analyzer system is properly apertured to accept incoming particles from a spot of 1.5 mm diameter at the sample and within a cone of 2.5 degrees half-angle. The lens system used has constant transmission independent of the incident energy. The energy analyzer is independently rotatable about two orthogonal axes, giving it complete freedom of access to any angle of collection relative to the sample orientation. The sample can rotate about two orthogonal axes so that any angle of incidence can be used. Specific examples are given of the performance of the system when used for the measurement of the angular distribution of photoelectrons excited by synchrotron radiation.