Cross-sections for electron-scattering from 2-methyl-1-buten-3-yne, C₅H₆, molecules

Cross-sections for electron collisions with the 2-methyl-1-buten-3-yne [H₂CC(CH₃)CCH] molecule were measured and calculated. Absolute grand-total electron-scattering cross-section (TCS) was taken at impact energies from 0.6 to 300 eV in the linear electron-transmission experiment. The TCS energy dependence for the electron–C₅H₆ collision has two prominent enhancements separated with a deep minimum located near 1.8 eV. In addition, in the low-energy TCS function two noteworthy features occur: (i) near 1 eV, a change in a slope on rapidly declining side of the TCS curve; (ii) between 2 and 5 eV, a distinct hump superimposed on the opposite, rising part of the curve. To search for the origin of these features in the TCS curve for C₅H₆, the comparison was made with results of the electron-scattering studies for selected hydrocarbon molecules. These features were attributed to the formation of short-living negative ions (resonant states). Elastic (ECS) and ionization (ICS) cross-sections for C₅H₆ and C₄H₂ (1,3-butadiyne) were computed up to 3 keV by means of the additivity rule (AR) approximation and the binary-encounter-Bethe (BEB) approach, respectively. For the C₅H₆ molecule, the sum ECS + ICS is in good agreement with the experimental TCS for energies above about 40 eV.