Collisions of Alpha-Particles with Carbon Nuclei

Abstract

More than 750,000 thorium (C+C′) alpha-particle cloud tracks have been photographed with a stereoscopic camera using a cloud chamber filled in one series with methyl-chloride and helium, and in another with acetylene and helium. For each series a range-velocity curve for carbon has been constructed by plotting the measured ranges, reduced to standard air values, against the calculated velocities for a total of 55 selected alpha-particle-carbon collisions. These curves are used for testing the validity of the method of reducing the ranges of heavy recoil nuclei in any gas to standard air values. Partial validity of the method has been observed in the present instance. An empirical relationship between the total mean straggling (in range), the atomic numbers of the atoms comprising the absorbing medium, and the atomic number of the recoil nucleus is presented. A brief analysis of the effectiveness of certain errors on the range-velocity results is given.