Electron-impact excitation of argon: I. The 4s´[½]1, 4p[½]1and 4p´[½]0states

We present absolute normalized differential cross sections (DCSs) for electron-impact excitation of the three individual electronic states of argon: 4s´[½] 1 , 4p[½] 1 and 4p´[½] 0 . The measurements were performed with incident electron energies of 16, 20, 30, 40, 50 and 80 eV, scattering angles between 5° and 150° and an angular resolution of better than 2°. The absolute scale for the reference state (4s´[½] 1 ) was established by experimental determination of inelastic-to-elastic intensity ratios for the 4s´[½] 1 state at the above impact energies. Absolute inelastic DCSs for the other two states were determined using the intensity ratios of the peaks in the energy-loss spectra. The absolute DCSs were extrapolated to 0° and 180° and integrated numerically to yield integral, momentum transfer and viscosity cross sections.