Tables 634-637 



RADIOACTIVITY, a PARTICLES 



TABLE 634.— Relative Ranges of a Particles of RaF in Gases 



5*3 



All values are at n. t. p.; the accepted value for the a particle in air is 3.721 cm and the 

 following values are merely relative. (After van der Merwe.) 



Gas 



Range, cm 



Molec. stopping 

 power 



Air H 2 H 2 CH 4 N 2 CO 2 N 2 3 C0 2 S0 2 CH 3 Br 

 3.58 16.28 .... 3.96 3.62 3.51 3.32 3.26 2.36 1.97 1.76 



1. 00 .22 .77 .91 .99 1.02 1.08 1. 11 1.52 1.82 2.04 



TABLE 635.— Relative Ranges of a Particles of RaC in Solid Elements 



(After Rausch von Traubenberg.) 



TABLE 635 (a). — Long-Range a Particles. Relative Numbers 

 Scintillations at abnormally great distances from thorium active deposit were first ob- 

 served by Rutherford-Wood. The range in air of the particles producing these was 11.3 cm 

 and it was shown by Rutherford that their mass was that of helium atoms, i. e., that they 

 were a particles. It now appears certain that some of the particles of long range must have 

 been H nuclei from Hydrogen or its compounds or protons from artificial disintegration. 



TABLE 636. — Atomic Stopping Powers, S, for a Particles of RaC, Z, Atomic Number 



(After Rausch von Traubenberg.) 

 The ability of atoms and molecules to stop a particles or, more briefly, their stopping 

 power, was first investigated by Bragg, and, more recently, by others. The atomic stopping 

 power for elements may be given by the formula S = RopoA/RpA , where R , p , A are the 

 range, density and atomic weight for the standard and R, p, A, the corresponding quantities 

 for the element considered. The stopping power therefore varies inversely as the range and 

 the density but directly as the atomic weight. 



TABLE 637. — Atomic Stopping Powers of Molecules for the a Particles of 

 RaC (84RaII) Relative to that of the Oxygen Atom 



(After Rausch von Traubenberg, Philipp.) 



Molecule 



Stopping power. 



H 2 (liquid) 

 1-53 



Smithsonian Tables 

 19 



