This problem, in the particular case of the hydrogen molecular ion, is so well known that a detailed reference to the large number of papers dealing with it is unnecessary. The investigations to which chief reference is made will be found at the end of this paper.
Abstract A large number of investigations have been carried out on the motion of charged particles through gases, and the subject has received added impetus from the introduction of quantum mechanics, as this theory is capable of dealing with collision phenomena in a manner that was beyond the reach of Bohr’s quantum theory. In the early days of the wave theory, many experiments were devised with a view to testing the validity of the theory; but now the foundations of quantum mechanics have been so firmly laid that we may use the theory to clarify the more complicated phenomena observed in the passage of charged particles through gases. Both from the experimental and theoretical point of view the most convenient particles to study are electrons; and, as a consequence, the phenomena observed in the collisions of electrons with gas molecules are well known and to a large extent understood. Well-marked diffraction phenomena have been observed and the relative probabilities of elastic and inelastic collisions measured for a number of gases. Although detailed theoretical explanations have not always been given, it is possible in nearly all cases to give a general description of the main processes contributing to the observed effects. For example, the Ramsauer effect is now completely explained.
In view of the recent experimental determination of the dispersion by atomic hydrogen it seems interesting to apply the theory of dispersion developed by Schrodinger to this case. In this paper we restrict ourselves to an approximation in which terms of the order of relativistic correction are neglected. For this purpose it is simpler to obtain our wave equation by the operational method of Schrodinger and Eckart, as extended by Epstein, for in this way we immediately obtain an equation free of relativistic terms. In what follows, in order to preserve a continuity of the discussion, details of calculations are omitted from the main text and are given as Supplementary Notes at the end of the paper. References will be found immediately preceding the Supplementary Notes.
Approximate expressions are obtained, when the distance R between the nuclei is very large, for that portion of the wave function in the two-centre problem which depends on the hyperbolic coordinate μ. From these expressions the number and the approximate position of the nodes in μ can be deduced and hence the rules can be found by which that state of the combined atom at R = 0 can be determined which corresponds to a given state of the atom when the nuclei are completely separated. These rules are also applicable to the cases where the two atoms which can be formed when the nuclei are completely separated have the same energy. The converse problem of finding what state of the completely separated atom corresponds to a given state of the combined atom at R = 0 can also be solved by the use of the rules.