Structures in dissociative electron attachment cross-sections in thymine, uracil and halouracils

Interaction of low-energy electrons with the pyrimidine bases and nucleosides of DNA

“…The yield curves for both of these anions show weak maxima near 0.3 eV. At higher energy, the ͑T-H͒ − yield closely resembles that observed in DA measurements on thymine itself, 7,11,12,16,17,21,[25][26][27]29 with a narrow peak near 1.0 eV and a broader maximum centered at about 1.7 eV, while the ͑2-deoxyribose-OH͒ − yield shows a single broad maximum centered near 1.2 eV. Since our calculations indicate only small shifts in the resonance positions between T and dT, the peak at 1.7 eV in ͑T-H͒ − yield from dT might be associated with the second * resonance, as has been suggested for the analogous peak in DA to T. 27 Likewise, the weak feature at 0.3 eV might be associated with trapping in the first * resonance.…”

“…33 However, comparatively few studies have directly examined low-energy electron scattering by the nucleobases, nucleosides, or nucleotides. To our knowledge, the only elastic cross section measurement to date is that by Abouaf and Dunet for uracil ͑and 5-bromouracil͒, 21 and their result is relative and limited to 90°scattering angle. No other differential elastic measurements, and no integral elastic or total scattering cross section measurements, appear to be available.…”

Interaction of low-energy electrons with the purine bases, nucleosides, and nucleotides of DNA

“…15,23,27 No gas-phase total or elastic scattering cross section measurements for the nucleobases have, to our knowledge, been reported, except for the relative 90°differential cross sections for uracil and halouracils obtained by Abouaf and Dunet. 21 However, Scheer et al 15 and Aflatooni et al 39 have conducted valuable studies of the electron-transmission spectra for the nucleobases that reveal the energies of resonances in the lowenergy total scattering cross section, and they have assigned the features they see to * shape resonances. The few calculations that have been made of electron cross sections for nucleobases have mostly relied on one-electron, potentialscattering models [40][41][42][43] and have produced low-energy elastic cross sections whose resonance positions disagree with the experimentally determined positions.…”

Low-energy electron collisions with gas-phase uracil

“…Gas-phase experiments [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] have explored electron collisions with molecular subunits including the purine and pyrimidine bases of DNA, 3,[5][6][7][10][11][12][13][15][16][17][18][19][20][21][22] the RNA base uracil, 7,10,11,13,[17][18][19]21,22 and halogenated derivatives. 5,[8][9][10]14,17 Most of these experiments have studied dissociative attachment 3,5-7,10-13,15-22 and/...…”

“…In uracil, for example, a strong feature is seen at 1.0 eV in the production cross section for ͑U−H͒ − ͑that is, the anion formed after removing one hydrogen from uracil͒, 7,10,11,13,[17][18][19]22 with weaker features at 0.7 and possibly 0.8 eV. It is natural to suspect the involvement of a shape resonance; however, these energies do not coincide with any of the ‫ء‬ resonance assignments of Burrow and co-workers, 4,10 and an alternative explanation in terms of vibrational Feshbach resonances built on the dipole-bound anion has been proposed.…”