Cross sections for ionization and ionic fragmentation of pyrimidine molecules by electron collisions

Total electron-scattering cross sections from pyrimidine as measured using a magnetically confined experimental system

“…At 50 eV, where both effects should be smallest within the overlapping energy range, a good agreement is found between the present σ expt (29.3 × 10 −20 m 2 ) and the sum of elastic integral CSs from Ref. [14] and ionization and electronic excitation CSs measured by Linert et al [18] and Jones et al [15], respectively (26.1 × 10 −20 m 2 ), especially when taking into account that in Ref. [15], electronic states are included up to an excitation energy of 10 eV and do thus represent rather a lower limit to the integral electronic excitation CS.…”

“…Jones et al [15,16] next measured differential electronic excitation CSs for various sets of unresolved states in the incident energy range 15-50 eV, while Hein et al [17] studied dissociative excitation from threshold up to 375 eV. Furthermore, Linert et al [18] have presented electron-impact ionization cross sections from threshold up to 150 eV. Electron energy loss spectra and the stopping power in pyrimidine (20-3000 eV) have also been published recently [19].…”

Ion induced fragmentation cross-sections of DNA constituents

“…The loss of one carbon or nitrogen atom would result in a mass group around 68 amu. As in previously reported studies on electron- [38][39][40], proton- [34] and photon-induced fragmentation [37,41], this group was absent in our spectra.…”

“…Mass 54 amu is assigned to the HCN fragment including the 13 C or 15 N isotope. Our data show a higher ratio than expected from the combined 3.9% isotopic abundance, probably because the contribution from the tail [34], the electron impact mass spectra of Linert (140 eV) [38], NIST [27] and of Wolff (400 eV) [34], and the photo-fragmentation mass spectrum of Vall-llosera (15.7 eV) [37]. of the 53 amu peak was not fully subtracted.…”

“…The data is compared to references [27,37,38]. In order to allow comparison to data by Wolff [34] the mass peak 79 amu from hydrogen loss and the isotopic mass peak 81 amu are added to the mass peak at 80 amu.…”