Total cross sections for electron and positron scattering from 4-fluorobenzaldehyde (C6H4(CHO)F) molecules

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A linear transmission time-of-flight method has been used to measure total cross sections (TCSs) for 0.4–1000 eV electron and 0.2–150 eV positron scattering from 4-fluorobenzaldehyde (C6H4(CHO)F) molecules. The disubstitution of the C6H6 parent molecule's two H atoms by the CHO radical and F atom in the 1- and 4-positions, on the benzene ring, has resulted in an electron TCS curve that shows that the original benzene ring symmetry has been partially preserved; a 1.6 eV peak corresponding to the 1.6 eV 2E2u C6H6 resonance peak, a 2.8 eV weak peak in contrast to a minimum for C6H6, a 4.6 eV shoulder corresponding to the 4.93 eV 2B2g resonance peak for C6H6, the main resonance peak centered at 8 eV corresponding to the 9.5 eV 2E1u main resonance peak for C6H6, and the characteristic change of the TCS slope producing a weak shoulder centered at 50 eV for both molecules. On the contrary the positron TCSs show low energy features that differ greatly from the parent C6H6 molecule; two relatively sharp peaks centered at 1 and 4 eV in contrast to the almost smooth and structureless 0.7–10 eV C6H6 peak. Nevertheless, these two positron TCSs resemble each other below 1 eV and above 6 eV.