Electron attachment to gas-phase uracil

Abstract

We present results about dissociative electron attachment (DEA) to gas-phase uracil (U) for incident electron energies between 0 and 14 eV using a crossed electron/molecule beam apparatus. The most abundant negative ion formed via DEA is (U-H)-, where the resonance with the highest intensity appears at 1.01 eV. The anion yield of (U-H)- shows a number of peaks, which can be explained in part as being due to the formation of different (U-H)- isomers. Our results are compared with high level ab initio calculations using the G2MP2 method. There was no measurable amount of a parent ion U-. We also report the occurrence of 12 other fragments produced by dissociative electron attachment to uracil but with lower cross sections than (U-H)-. In addition we observed a parasitic contaminating process for conditions where uracil was introduced simultaneously with calibrant gases SF6 and CCl4 that leads to a sharp peak in the (U-H)- cross section close to 0 eV. For (U-H)- and all other fragments we determined rough measures for the absolute partial cross section yielding in the case of (U-H)- a peak value of sigma (at 1.01 eV)=3 x 10(-20) m2.

Elastic and inelastic low-energy electron collisions with pyrazine

“…Our calculations also show the presence of a larger than expected number of core-excited resonances. This result is however, compatible with experimental evidence 13 for the presence of many resonances (more accurately, peaks in the yield of various anions) in the 5-10 eV range in uracil. These resonances do not necessarily have a single parent state.…”

“…Apart from the well-studied lower energy region, the total DEA cross section for the pyrimidinic DNA bases also shows a significant enhancement in the higher-energy range (from 5 eV to 9 eV), [13][14][15] comparable in magnitude to the one observed at the lower energies, which is thought to be caused in this case by core-excited resonances. 15,16 Recent measurements 17 of the electronic excitation cross sections of cytosine by low energy electrons have also provided evidence for the presence of higher-lying core-excited resonances in this system.…”

“…b) Electronic mail: j.gorfinkiel@open.ac.uk. served products 13 of the electron-uracil collision can also be explained by an interaction between the higher-lying (above 8 eV) dissociative σ * resonance and the lower-lying π * resonances.…”

Selective Bond Cleavage in Potassium Collisions with Pyrimidine Bases of DNA

“…The C 2 H − formation requires multiple bond breaking in the precursor anion. However, C 2 H has a considerable high electron affinity (2.969 eV), 38 which can explain being observed at all collision energies.…”

Low-energy electron collisions with gas-phase uracil

“…This discovery inspired numerous experiments aimed at elucidating various aspects of the electron-DNA interaction. 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,…”