Published online by Cambridge University Press: 24 October 2008
Much attention has been focused on the excitation of atomic spectra by electrons whose velocities do not greatly exceed the critical value, and it is now possible to form a rough idea of the behaviour of the “excitation function,” or probability that an electron of given velocity shall excite on impact, when the energy of the electron is only slightly greater than that required for excitation. But the form of this excitation function for much higher velocities is still in considerable doubt.
* Proc. Roy. Soc. 104, p. 480 (1923).CrossRefGoogle Scholar
* I am deeply indebted to Prof. Barnes for his courtesy in allowing me to use his instrument and also to Mr C. Thomas for his help in measuring some of the plates on the Princeton photometer.Google Scholar
† In conversation with Prof. Born I have gathered that he expects no great change in the form of the function when applied to atoms other than hydrogen.Google Scholar
‡ Born, , “Zur Wellenmechanik der Stossvorgänge,” Göttinger Nachrichten, p. 146 (1926).Google Scholar
* Zeit. f. Phys. 28, p. 411 (1926).Google Scholar
† Dymond, , Physical Review, 29, p. 433 (1927); this will be referred to as “Electron Scattering.”CrossRefGoogle Scholar
* Loc. cit.Google Scholar
† I am deeply indebted to Professor Franck for pointing oat to me the possibility of this type of excitation of light. In the course of correspondence he has very kindly informed me of the possibility of recombination of a positive ion with the electron which has been removed to form it, before that electron has had time to recede from the sphere of influence of the ion. This of coarse is a radically different process from the recombination of an ion with a “free” electron, for which no sound experimental evidence has been adduced.