MEASUREMENTS OF THE MOLECULAR STOPPING CROSS-SECTIONS OF ORGANIC RING COMPOUNDS

The molecular stopping cross sections of the organic ring compounds cyclopentane, cyclohexane, cyclooctane, cyclopentene, cyclohexene, 1,3-cyclohexadiene, benzene, toulene, phenylacetylene, cyclohexanone, and p-dioxane have been measured for helium ions with energies from 0.3 to 2.0 MeV. It is found that the ring structure of molecules with less than six CH 2 groups in the ring as well as the nature of the bonds involved correlate with deviations from Bragg's rule as great as 14.7%. Evidence of resonance in the ring structure which correlated with the stopping cross section of the compound benzene is also observed. A qualitative relationship between chemical bond strain and deviations from Bragg's rule is given.