Joseph John Thomson

“ Oxygen gives a series spectrum, a spark spectrum which has not been resolved into series, and some banded spectra. All these spectra are emitted when oxygen positive rays pass through oxygen, the spark spectrum being the brightest With oxygen it is the spark lines that show the Döppler effect. ”

“ In the positive rays in hydrogen the molecules frequently outnumber the atoms, but no radiation that can be attributed to the molecules has yet been detected.The spectrum of hydrogen is there, but as it does not show the Döppler effect it cannot be due to the molecules. ”

“ The pressures at which spectroscopic observations have been made are so high that an atom is continually passing backwards and forwards between the neutral and charged conditions. It is thus a matter of great difficulty to determine whether the atom emits the lines in one state or the other, and there Is, I think, at present no experiment which is absolutely decisive between the two views. Thus, for example, it is found that the Doppler effect is increased when the positive rays are exposed to an accelerating potential after passing through the cathode. ”

“ The corpuscle falls into the positively charged atom and the energy gained by the fall is radiated away as light. On this view the intensity of the light should vary with the number of recombinations of positive ions and negative corpuscles. Let n be at any instant the number of neutral particles per unit volume moving velocity V, p the number of positive particles moving with the same velocity, N the number of corpuscles In the tract of these particles per unit volume. ”

“ Stark1 had discovered a property of the positive rays which Is of great Importance In connexion with the origin of spectra, and Incidentally has led to results which have confirmed some of those obtained by the newer methods. ”

“ An example of this is shown in Fig. 17, Plate I. The intensity curve corresponding to the Doppler effect ought to have the same type of variations in intensity as these parabolas, and a beaded parabola ought to give rise to a Doppler curve with as many maxima as there are beads on the parabola. Sometimes these beads on the parabolas are quite numerous.
It is remarkable that the parabola corresponding to the atom of hydrogen is often beaded in such a way that the velocity of the particles producing one bead is to that producing the other as . ”

“ This velocity is small compared with the average velocity of the positive rays of hydrogen; it corresponds to a fall through a potential difference of less than 100 volts. It Is comparable In value with that which the mercury atom acquired In many of the experiments represented by the preceding photographs, when It had possessed one but only one charge throughout Its journey through the discharge tube. The maximum displacement of the line depends to some extent on the potential difference between the terminals of the discharge tube ”