Inelastic collisions of the uracil molecules with electrons.

Ionization and excitation of the uracil molecules by electron impact is investigated. Production of positive ions of uracil molecules (nucleic acid base) was studied using a crossed electron and molecular beam technique. The method developed by the authors enabled the molecular beam intensity to be measured and the electron dependences and the absolute values of the total cross sections of production of both positive ions to be determined. It is shown that the total positive uracil ion production cross section reaches its maximal value of (1.0 ± 0.1) × 10-15 cm2 at the 95 eV electron energy. Dissociative ionization cross sections were also determined. The luminescence spectra of isolated uracil molecules in the wavelength range of 200-500 nm under the influence of slow electrons are obtained. In the spectrum, more than 20 spectral bands and lines at 100 eV electron energy are observed. It is shown that the uracil radiation spectrum is formed by the processes of molecules dissociative excitation, dissociative excitation with ionization, excitation of electronic levels of the initial molecule and molecular ion. [ABSTRACT FROM AUTHOR]