Energy distributions of electrons emitted from GaAs(Cs, O)

A method to map out the energy distribution N(E∥,E⊥) of an electron beam as a function of the longitudinal (E∥) and transverse (E⊥) energy has been developed and applied to study the photoemission process from GaAs(Cs, O) at 90 K. The method proceeds by “marking” electrons with fixed longitudinal energy E∥b and a subsequent measurement of the associated differential transverse energy distribution N⊥(E∥b,E⊥), applying an adiabatic magnetic compression technique. The complete energy distribution N(E∥,E⊥) of electrons from a GaAs(Cs, O) photocathode obtained by a stepwise variation of E∥b provides details about the transfer of electrons through the GaAs(Cs, O)–vacuum interface and demonstrates that not only electron energy loss, but also elastic electron scattering is of crucial importance in the escape process.