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.