Abstract
Relative differential electron-impact cross sections have been measured for elastic scattering for excitation of the 3d104p 2 P1/2,3/2, 3d94s2 2D5/2 and 3d94s2 2D3/2 states of Cu at 6, 10, 20, 60 and 100 eV in the 0 degrees to 140 degrees angular range. The relative values were normalised to the absolute scale by utilising He as a secondary standard for determining the correct energy dependence and by accepting the value of the calculated elastic differential cross section at 100 eV, 40 degrees as 1.28*10-16 cm2 sr-1. Integral and momentum-transfer cross sections have been obtained by extrapolation to 180 degress. The cross section for the excitation of the 2P state is large compared to that for elastic scattering, and population inversion in this state with respect to the 2D state is readily achieved by electron impact. None of the theoretical predictions utilising classical, Born or static-exchange approximations agree with the experimental results at low impact energies.