Electron impact excitation of argon in the extreme vacuum ultraviolet

Polarization-free excitation cross sections in the extreme vacuum ultraviolet have been measured for electron impact on Ar. Observed spectral features were those lines of Ar I and Ar II which lie between 700 and 1100 A. Excitation functions were measured for the Ar I resonance line at 1048 A and the Ar II resonance line at 920 A. Peak cross sections for these two lines were found to be (39.4 +- 7.9) x 10/sup -18/ and (6.9 +- 1.4) x 10/sup -18/ cm2, respectively. At low energies, excitation of the Ar II resonance line is dominated by an electron exchange transition