Соударения медленных электронов с молекулами тимина

Using a hypocycloidal electron spectrometer, the total scattering cross section of slow (0–9 eV) electrons and the dissociative electron attachment cross section for thymine molecules in the gas phase were measured. The ionization cross section for a thymine molecule was studied in the energy range of 9–32 eV. Some features were found in the scattering cross section, caused by the formation and decay of short-lived states of the molecular negative ion. Three of them ( E = 0.32, 1.71, and 4.03 eV) relate to shape resonances; the others, which are observed for the first time, refer to the Feshbach resonances (or core-excited resonances). In the total dissociative attachment cross section in the energy range of E < 4 eV, a clear structure is observed due to the formation of a negative ion (T–H)^–, and a less intense structure associated with the total contribution of fragment thymine ions is found above 4 eV. The correlation of the features found in the total scattering cross section and in the dissociative attachment cross section is assessed. The absolute total scattering cross section was obtained by normalizing the measured curve to the theoretical calculation. In the total ionization cross section, features are observed that are associated both with the effect of the formation of fr-agment ions and with ionization due to the ejection of electrons from the orbitals of the outer shell of the molecule.

Electron Attachment to Metallic Clusters

The calculations of the low-energy attachment cross section to metallic clusters are investigated. Low energy electrons are taken as slow enough to excite a giant dipole collective resonance within the cluster. The calculations are more refined than the earlier ones – they do not depend on the experimental data, and we improved RPAE calculation of the collective resonance in the cluster. The results are interesting for the nano-region and designing of new materials.

THE STRUCTURAL AND VIBRATIONAL PROPERTIES OF C60 ADSORBED ON THE GRAPHITE(0001) SURFACE

The exciting opportunities promised by the unique properties of C60 can only be fully exploited if the growth and properties of this material can be understood. To this end we have carried out a study of the structural and vibrational properties of C60 adsorbed on the graphite(0001) surface. We observed a novel high-order periodicity at monolayer coverages which indicates that even the weak corrugation potential of the surface can perturb the geometry of the overlayer. Vibrational spectra show a low-energy resonance in the inelastic scattering cross section which we correlate with a resonance feature observed in the electron attachment cross section of C60. The lack of a measurable perturbation in the resonance upon going from multilayer to monolayer coverage indicates that a weak physisorption bond exists between the molecules and the surface.