Electronic Excitation of Molecules by Electron Impact

Abstract

In this talk I will review the recent progress that has been made in the theoretical determination of differential and integral cross sections for the electronic excitation of molecules by low-energy electrons. Whereas there has been considerable progress in the development and application of theoretical methods for treating inelastic electron-atom scattering [1], the situation is quite different for the related molecular problem. It is well-known that this difference is ultimately due to the difficulties associated with the nonspherical nature of the electron-molecule force field. In fact, it was not until the 1960’s that a renewed interest in processes involving H2 and N2 resulted in the application of plane-wave theories to treat the excitation of electronic states in these molecules. In the last five years more advanced theories such as the distorted-wave method, the impact-parameter method, and the close-coupling method have been applied to the description of electron impact excitation of diatomic molecules. The results of these more recent applications, and their comparison with available experimental data, will be the focal point of my presentation. We will see that, although the results of some of these theoretical applications are encouraging, there are substantial disagreements between both the predictions of the different methods themselves, and with the experimental data. There clearly remains a serious need for further development of theoretical methods for the prediction of electron impact excitation cross sections of both linear and polyatomic molecules.