Excerpt from A Variational Calculation of the Elastic: Scattering of Electrons, by Hydrogen Atoms One of the important problems of upper atmospheric and astrophysical research is the determination of the frequencies of collisions between electrons and atomic systems. Informa tion on this subject can be obtained from a knowledge of the total cross-section, Q, and to some extent from the differential cross-section, (hg), of the collision. The temperatures at which these collisions occur are of such a magnitude that the electron energies are of the order of a fraction of an electron volt, and at these low energies the problems associated with experimental determinations of the cross-sections become complex. Consequently there is a deficiency of experimental data. It is therefore essential to have theoretical methods for calculating the cross-sections. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.