Nobel prize to C. T. R. Wilson awarded in 1927 "for his method of making the paths of electrically charged particles visible by condensation of vapour''. Co-winner A. H. Compton "for his discovery of the effect named after him''
Wilson, C.T.R.; Investigations on X Rays and Rays by the Cloud Method. Part 1. - X Rays.
Proc. Roy. Soc. A104 (1923) 1;
The experiments so far have been confined almost entirely to air. The track of the electron ejected from an atom which emits a quantum of radiation, and that of the electron ejected from the atom which absorbs the radiation, can be identified. The primary action of X radiation ( < 0.5Å) gives ray tracks with initial kinetic energy comparable to a quantum of the incident radiation; and tracks of very short range; the
latter electrons are ejected nearly in the direction of the primary X rays; they are probably related to the phenomena which have led to the postulation of a "J'' radiation. The rays frequently occur in pairs, or groups, of which five classes have been distinguished. The pairs probably consist of one K-electron, ejected by the primary X rays, and a second by the combined action of primary radiation, and of the K radiation from the atom from which the first
electron was ejected. Range measured along track approximately is proportional to 4th power of velocity for ranges of 0.5 cm to 1.5 cm. Primary ionization is about 90 per cm for a velocity of 1010 cm per sec.; it varies approximately inversely as the square of the velocity. Total ionization per cm is about 3 or 4 times the primary. Primary ionization agrees with J. J. Thomson's theory, if the minimum energy of ejection is about 7 volts, approximately the resonance potential (not ionization)
of N. The number of tracks with nuclear deflections over 90° agrees with Rutherford's theory, and gives for the charge of the nucleus 6.5e, almost identical with the actual nuclear charge of N = 7e. Many features of the ray tracks, including the curvature which sometimes appears, may be due to radiations excited in atoms by the passage of the rays. The radiations continually overtaking the
particle and affecting the subsequent collisions. For other results of the observations the original paper should be consulted. (Science Abstracts, 1923, 2213, H. N. A.).
Related references More (earlier) information appears in C. T. R. Wilson, Proc. Roy. Soc. A85 (1911) 285;
C. T. R. Wilson, Proc. Roy. Soc. A87 (1912) 277;
More (later) information appears in C. T. R. Wilson, Proc. Roy. Soc. A104 (1923) 192;
atom ion e
Experimental confirmation of the ionization process predicted by Compton for a corpuscular photon.