Electron impact excitation at forward scattering

At forward scattering, the recent generalized Lassettre expansion using a single real Regge pole, the momentum dispersion method (MDM) of Haffad er al and the forward scattering function of Avdonina et al all yield results for H 1s-2p excitation that agree excellently with those obtained by the convergent close-coupling approximation of Pray et al down to about twice the threshold energy. Measured electron impact data for Cd and Xe are used to demonstrate the utility of the analytical continuation in energy and angle of the MDM and to guide measurements in the difficult to measure angular regime near and at zero scattering angles.