Electron ranges in liquid alkenes, dienes, and alkynes: Range distribution function in hydrocarbons

Free ion yields have been measured as functions of temperature T and electric field strength E in hydrocarbon liquids. A range distribution of the secondary electrons in hydrocarbons, suitable for use in the one‐ion‐pair‐per‐spur model, is $$\begin{array}{c}{\text{F(y)=(4y}}^2{\mathrm{/\pi }}^{\text{1/2}}{b}_{\mathrm{GP}}^3)\exp {\mathrm{(-y}}^2{\mathrm{/b}}_{\mathrm{GP}}^2{\text{),\hspace{0.17em}y<2.4\hspace{0.17em}b}}_{\mathrm{GP}};\\ {\text{F(y)=(4y}}^2{\mathrm{/\pi }}^{\text{1/2}}{b}_{\mathrm{GP}}^3)\exp {\mathrm{(-y}}^2{\mathrm{/b}}_{\mathrm{GP}}^2{\text{)+0.5(b}}_{\mathrm{GP}}^2{\mathrm{/y}}^3{\text{),\hspace{0.17em}y>2.4\hspace{0.17em}b}}_{\mathrm{GP}};\end{array}$$ where F(y)dy is the fraction of thermalized electron‐ion pairs that have initial separation distances between y and y+dy, and b_GP is the dispersion parameter. This equation is suitable for all of the liquids that have been studied thus far, at all values of T and E that have been used. The value of b_GPd for a given liquid is independent of T, where d is the liquid density. The density‐normalized ranges in a family of hydrocarbons with the same number of carbon atoms and analogous carbon skeletons decrease in the order alkane>alkene‐1>alkyne‐1. Two terminal double bonds are more effective than one terminal triple bond in reducing the electron range. Conjugation of the double bonds appears to have no special influence on electron de‐energization. The range in a trans‐alkene‐2 is essentially the same as that in the corresponding alkene‐1, but otherwise, internal double bonds are less effective than terminal double bonds in de‐energizing the electrons. Ranges in cis‐alkenes are greater than those in the corresponding trans‐alkenes. Increasing the amount of chain branching in a family of alkanes or alkenes increases the electron range. An internal triple bond increases the range over that in an alkane.