Rydberg electron transfer to CH3NO2: Lifetimes and characteristics of the product CH3NO2− ions

Negative ion formation in potassium-nitromethane collisions

Ion-pair formation in gaseous nitromethane (CH(3)NO(2)) induced by electron transfer has been studied by investigating the products of collisions between fast potassium atoms and nitromethane molecules using a crossed molecular-beam technique. The negative ions formed in such collisions were analysed using time-of-flight mass spectroscopy. The six most dominant product anions are NO(2)(-), O(-), CH(3)NO(2)(-), OH(-), CH(2)NO(2)(-) and CNO(-). By using nitromethane-d(3) (CD(3)NO(2)), we found that previous mass 17 amu assignment to O(-) delayed fragment, is in the present experiment may be unambiguously assigned to OH(-). The formation of CH(2)NO(2)(-) may be explained in terms of dissociative electron attachment to highly vibrationally excited molecules.

Steric Asymmetry in Electron Transfer from Potassium Atoms to Oriented Nitromethane (CH3NO2) Molecules

Electrons are transferred in collisions between potassium atoms and CH(3)NO(2) molecules that have been oriented in space prior to collision. The electron transfer produces K(+) ions, parent negative ions CH(3)NO(2)(-), and the fragment ions e(-), NO(2)(-), and O(-) in amounts that depend on the energy. The positive and negative ions are detected in coincidence by separate time-of-flight mass spectrometers at various collision energies for both CH(3)-end attack and NO(2)-end attack. The steric asymmetry for electrons and CH(3)NO(2)(-) is essentially zero, but the steric asymmetry for NO(2)(-) shows that NO(2)(-) is formed mainly in CH(3)-end collisions. There is evidence that the electrons and NO(2)(-) have the same transient precursor, despite having different steric asymmetries. It appears likely that the precursor is formed by electron transfer mainly in collisions normal to the molecular axis leading to near zero steric asymmetry for the electron. This transient precursor can also eject an NO(2)(-) ion, which is more likely to be removed as KNO(2) salt when K(+) ions are near the NO(2) end of the molecule, with the result that CH(3)-end collisions seem to produce more NO(2)(-).

Rydberg electron transfer to C6H5NO2: lifetimes and characteristics of the product C6H5NO2- ions

The nature of electron binding in C6H5NO2- ions produced by Rydberg electron transfer in K(np)C6H5NO2 collisions is investigated through measurements of the number and the lifetimes of the product ions and their dependence on Rydberg atom velocity and principal quantum number n in the range 12 <or approximately n <or approximately 30. The data are interpreted by comparison to results obtained using well-known dipole-bound and valence-bound anions. At high n direct capture into valence-bound states with a lifetime of approximately 1.6 ms is observed. At low n the data suggest that, while direct capture into valence-bound states is still possible, the majority of the observed C6H5NO2- ions result from the onset of a second reaction channel that involves the formation of a dipole-bound "doorway" state that rapidly evolves into a state with predominantly valence-bound character. These findings are discussed in the light of earlier work on electron binding to C6H5NO2.

Electron Binding to Nucleic Acid Bases. Experimental and Theoretical Studies. A Review

An in-depth knowledge of an excess electron binding mechanism to DNA and RNA nucleobases is important for our understanding of radiation damage influence on the biological functions of nucleic acids, as well as for the possible use of DNA molecules as wires in molecular electronic circuits. The of anions created by electron attachment to individual nucleic acid bases is discussed in detail. The principles of the experimental and theoretical approaches to the description of these anions are outlined, and the available results concerning valence- and dipole-bound anions of nucleic acid bases are reviewed. A review with 167 references.