Published online by Cambridge University Press: 24 October 2008
From measurement of tracks formed in an expansion chamber range distribution curves are obtained relative to 2134 α particles from thorium C′ and 729 α particles from radium C′. These curves exhibit marked differences in the proportion of short range particles which each contains. The origin of these differences is discussed. Estimates are made of the linear straggling coefficients relative to the absorption of the two groups of particles in air (in the experimental arrangement other media entered as well). These results very definitely confirm the conclusions reached by Briggs from measurements of the straggling of velocity of the particles. The sources of error which enter when the expansion chamber is used for the measurement of straggling coefficients are briefly reviewed.
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