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

A method to map out the energy distribution N(E-parallel to,E-perpendicular to) of an electron beam as a function of the longitudinal (E-parallel to) and transverse (E-perpendicular to) energy has been developed and applied t o study the photoemission process from GaAs(Cs, O) at 90 K. The method proc eeds by "marking" electrons with fixed longitudinal energy E-parallel to(b) and a subsequent measurement of the associated differential transverse ene rgy distribution N-perpendicular to(E-parallel to(b),E-perpendicular to), a pplying an adiabatic magnetic compression technique. The complete energy di stribution N(E-parallel to,E-perpendicular to) of electrons from a GaAs(Cs, O) photocathode obtained by a stepwise variation of E-parallel to(b) provi des details about the transfer of electrons through the GaAs(Cs, O)-vacuum interface and demonstrates that not only electron energy loss, but also ela stic electron scattering is of crucial importance in the escape process. (C ) 2001 American Institute of Physics.