Electron collisions with methyl-substituted ethylenes: Cross section measurements and calculations for 2-methyl-2-butene and 2,3-dimethyl-2-butene

摘要

We report electron-scattering cross sections determined for 2-methyl-2-butene [(H3C)HC=C(CH3)(2)] and 2,3-dimethyl-2-butene [(H3C)(2)C=C(CH3)(2)] molecules. Absolute grand-total cross sections (TCSs) were measured for incident electron energies in the 0.5-300 eV range, using a linear electron-transmission technique. The experimental TCS energy dependences for the both targets appear to be very similar with respect to the shape. In each TCS curve, three features are discernible: the resonant-like structure located around 2.6-2.7 eV, the broad distinct enhancement peaking near 8.5 eV, and a weak hump in the vicinity of 24 eV. Theoretical integral elastic (ECS) and ionization (ICS) cross sections were computed up to 3 keV by means of the additivity rule (AR) approximation and the binary-encounter-Bethe method, respectively. Their sums, (ECS+ICS), are in a reasonable agreement with the respective measured TCSs. To examine the effect of methylation of hydrogen sides in the ethylene [H2C=CH2] molecule on the TCS, we compared the TCS energy curves for the sequence of methylated ethylenes: propene [H2C=CH(CH3)], 2-methylpropene [H2C=C(CH3)(2)], 2-methyl-2-butene [(H3C) HC=C(CH3)(2)], and 2,3-dimethyl-2-butene [(H3C)(2)C=C(CH3)(2)], measured in the same laboratory. Moreover, the isomeric effect is also discussed for the C5H10 and C6H12 compounds. (C) 2015 AIP Publishing LLC.