Electron energy loss distributions in solid and gaseous hydrocarbons

The dipole oscillator strength distributions for solid and for gas phase cyclohexane, cyclohexene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, and benzene were constructed from experimentally derived optical constants and from atomic X-ray absorption cross sections. Monte Carlo simulations of the energy loss by electrons of initial energy from 10 keV to 1 MeV in these media were performed using cumulative inelastic cross sections obtained from a formulation incorporating the constructed dipole oscillator strength distributions. In the solid phase, the energy loss distributions, the most probable energy losses, and the mean energy losses for electrons show little effect due to the conjugation of π bonds. However, there are large differences between the gases, and there is a considerable effect due to condensation. The most probable and the mean energy losses for 1 MeV incident electrons in solid cyclohexane, cyclohexene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, and benzene are in the ranges 22-24 and 47-48 eV, respectively. Comparison with data for water suggests that the values for the solid phases of hydrocarbons are acceptable approximations for the liquid phase. Density normalized stopping powers, inelastic mean free paths, and ranges for electrons in the various hydrocarbons are also presented.