Estudo teórico e experimental da interação de elétrons com moléculas de interesse astroquímico

Abstract

We performed a theoretical and experimental investigation on electron (e⁻) scattering by molecules of astrochemical interest. Theoretically, we obtained elastic differential (DCSs), integral (ICSs) and momentum-transfer (MTCSs) cross sections, total (TCSs) and total absorption (TACSs) cross sections for electron collisions with cyanoacetylene (HC₃N), acetonitrile (CH₃CN), isocyanic acid (HNCO), chloroform (CHCl₃), and chlorobenzene (C₆H₅Cl) molecules in the 0.1 to 1000 eV incident electron energy-range (E₀) by using ePolyScat codes (D and E3 versions). Presently, important developments in E3 version were performed in order to include the account of absorption effects (already present in D version). Thus, one uses a complex optical potential to represent the e⁻-molecule dynamics. In the methodology applied by ePolyScat, the wave function and the interaction potentials are single-center expanded, and the scattering equations are solved iteratively with the Padé’s approximants technique. The effectiveness of the modification in ePolyScat-E3 is verified by the good agreement with experimental data and other theories. Calculations were also performed using the independent atom model (IAM). Experimentally, DCSs data were obtained for E₀ from 20 up to 800 eV applying the relative flow technique (RFT) for chloroform and chlorobenzene. In the E₀ < 50 eV region, DCSs data were also measured at CSUF by Prof. M. A. Khakoo in collaboration, allowing the comparison between the theoretical and experimental data in a large energy range (0.5 ≤ E₀ ≤ 800 eV). Obtaining DCSs for non-chlorinated molecules was made impossible by COVID-19 pandemic. Nonetheless, a significant experimental advance was performed, making possible the synthesis of HC₃N samples at UFSCar. For such molecule, we obtained but one set of DCSs at E₀ = 20 eV. We generally observe a good agreement between the theoretical and experimental results obtained in the present work and other data available.