. The Bell System technical journal . tra every spot or line of which is the evidenceof a separate isotope of the element in question. Germanium andzinc are neither the least nor the most profuse in isotopes among theelements; there are still a few (fluorine and sodium, for instance) forwhich only one has been discovered, and at the other extreme there istin with no fewer than eleven. It is, of course, the charge-to-mass ratio of the ion rather than itsmass which is deduced from the position of the spot and the strengthsof the accelerating and deflecting fields. (There is no need of givingthe
. The Bell System technical journal . tra every spot or line of which is the evidenceof a separate isotope of the element in question. Germanium andzinc are neither the least nor the most profuse in isotopes among theelements; there are still a few (fluorine and sodium, for instance) forwhich only one has been discovered, and at the other extreme there istin with no fewer than eleven. It is, of course, the charge-to-mass ratio of the ion rather than itsmass which is deduced from the position of the spot and the strengthsof the accelerating and deflecting fields. (There is no need of givingthe formula here, as it is to be found in every textbook and is readily CONTEMPORARY ADVANCES IN PHYSICS 311 derived.) The charge is usually + e (singly-ionized atom), sometimes+ 2e (doubly-ionized atom), rarely + 3e or greater; there is nodifficulty in telling which. No one goes to the trouble of determiningmass or charge-to-mass ratio absolutely, with the full precision ofwhich the method might be capable; what is actually evaluated is. 54 66 67 68 70 Fig. 4—Mass-spectrum of zinc (K. T. Bainbridge). the ratio of the mass of each unknown to that of some familiar kindof atom, eventually always the atomic mass of the principal isotopeof oxygen. There are various schemes and tricks for facilitating thecomparisons, of interest chiefly to those who have some intention ofimitating the experiments. Of more general interest is the problem ofproducing the ions. The elements which are gaseous at ordinary temperatures, and thosewhich have compounds that are gaseous at ordinary temperatures(such as carbon in CO and CO2), and the metals which have high vapor-pressures such as mercury—these were analyzed early in the game. i li I I 76 74 73 72 70 Fig. 5—Mass-spectrum of germanium (K. T. Bainbridge). They are introduced into the discharge-tube, alone or mixed withother gases, and the processes of the discharge ionize their atoms(or the molecules of their compounds, which serve the purpose
Size: 3254px × 768px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
