New Data on the Artificial Transmutation of Elements.

E. Rutherford and J. Chadwick. The desintegration of Elements by α-Particles. Nature 107, p. 41 (1921).

The improved optics of the apparatus allowed Rutherford to make a number of new observations on the artificial decomposition of elements. It turned out that α-particles with a range of 7 cm.²) produce in hydrogen H-particles with a range of 29 cm., but H-particles arising from nitrogen exhibit a range of 40 cm. Particles with a greater range could also be observed in other substances besides nitrogen. Thus particles with a range greater than 40 cm. were observed in boron, fluorine, sodium, aluminum, and phosphorus. It is especially interesting that particles with a range of approximately 80 cm. arise from aluminum. The number of particles in boron and sodium is considerably smaller than in the other elements.

In Li, Be, C, O, Mg, Si, S, Cl, K, Ca, Ti, Mn, Fe, Cu, Sn, Ag, if the action of α-particles was observed at all, it was very weak. It is determined

²) All numerical data for ranges refer to air.

no occurrence was observed of particles with ranges greater than 32 cm in O, CO₂, and SO₂. Neither the nature of these particles with large ranges, nor the dependence of their number, distribution, and range on the velocity of the incident α-particles has yet been investigated. Comparing all the results, one may conclude that only elements with atomic weights expressed by the general formulas \(4n+3\) or \(4n+2\), and moreover not greater than 31, undergo disintegration; elements of the \(4n\) series, however, do not yield particles with large ranges.

E. Shpolsky.