Differential cross sections for the electron impact excitation of pyrimidine

Abstract

We report on differential cross section (DCS) measurements for the electron-impact excitation of the electronic states of pyrimidine. The energy range of the present measurements was 15-50 eV with the angular range of the measurements being 10 • -90 • . All measured DCSs displayed forward-peaked angular distributions, consistent with the relatively large magnitudes for the dipole moment and dipole polarizability of pyrimidine. Excitations to triplet states were found to be particularly important in some energy loss features at the lower incident electron energies. To the best of our knowledge there are no other experimental data or theoretical computations against which we can compare the present results.

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.…”

“…[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. Generally, it has to be kept in mind that the integral elastic CS derived in Ref.…”

“…Subsequently two experimental groups [13,14] published elastic differential cross sections (DCSs), presenting results for the combined energy range 3-300 eV. 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.…”

Cross-section calculations for positron scattering from pyrimidine over an energy range from 0.1 to 10000 eV

“…In the case of positron scattering, the experiments are also expected to encounter similar difficulties, plus some additional problems due to the significantly reduced incident positron fluxes. This is reflected in the available data for pyrimidine found in the literature: whereas electron collisions have been the subject of numerous studies, including the measurement of elastic differential cross sections [17,18], gas-phase electronic-state cross-section studies [19,20] and (e,2e) ionization studies [21], vibrational and electronic excitation cross sections in the condensed phase [22], and electron energy-loss spectra [23], little work on positron scattering from pyrimidine has been done. However, Zecca et al [24] measured total cross sections (TCSs) from 0.3 to 45 eV using a positron transmission beam technique.…”

Integral cross sections for electron impact excitation of vibrational and electronic states in phenol

“…[11][12][13][14][15][16][17][18] As a consequence, in this short paper, we report on our derivation of vibrational-mode and electronicstate ICSs from our previously published differential cross section measurements. 21,22 Phenol also possesses a range of physico-chemical properties which, from our experience with other collision systems, [24][25][26][27][28][29][30] are anticipated to play important roles in its scattering dynamics. Specifically, phenol has a permanent dipole moment of magnitude ∼1.42 D 3 and a significant average dipole polarisability of 10.53 Å 3 .…”