Scattering of electrons by a 1,2-butadiene (C4H6) molecule: measurements and calculations

Abstract

We present the results of experimental and theoretical study on electron collisions with a 1,2-butadiene (H2C=C=CHCH3) molecule. Absolute grand-total cross sections (TCSs) were measured using a linear electron-transmission method for collision energies in the 0.5–300 eV range. Two distinct features in the TCS energy curve were detected: a narrow peak located at 2.3 eV and a broad enhancement centered around 9 eV. We attributed these features to the formation of negative-ion resonant states, based on comparisons with the existing data for other targets of similar structure. Experimental findings indicate a bonding effect on the TCS when confronting TCS curves for allenes with those for respective acetylenes. Clear differences in experimental TCS energy dependences for C4H6 isomers (1,2-butadiene, 1,3-butadiene, 1-butyne and 2-butyne) show on the isomeric effect. The independent atom approximation was employed to calculate the elastic (ECS) cross section from 25 to 3000 eV, while the binary-encounter-Bethe approach was used for computation of the ionization (ICS) cross section, from the threshold up to 3 keV. The sum of computed cross sections (ECS+ICS) quite reasonably reproduces the experimental TCS values above 35 eV. The reported TCS experimental values are not corrected for the forward-angle scattering effect.