Electron-atom scattering at intermediate energies

A new method of calculating elastic and inelastic cross sections for electron-atom and electron-ion scattering at intermediate energies is described. In this method the total wavefunction is expanded as a sum over channel functions plus a sum over L2 integrable functions. Cross sections between channels included in the first expansion are obtained by averaging the T matrix over pseudo-resonances arising from the L2 integrable functions included in the second expansion. It is shown that an appropriate averaging procedure allows for loss of flux into open channels which are omitted from the first expansion. The method is discussed in detail for a two-channel model and is shown to give good results for elastic scattering in this case when only a few L2 integrable functions are included. The method is then applied to the astrophysically important transition 2s21Ssup(e)-2s2p3Psup(o) in CIII where the cross section at intermediate energies is found to be substantially below the previous best estimates