Absolute differential cross sections for elastic scattering of electrons from pyrimidine

Abstract

Differential cross sections ͑DCSs͒ for elastic scattering of electrons from pyrimidine ͑C 4 H 4 N 2 ͒ are presented for incident energies from 50 to 300 eV. The measurements were performed using a cross beam technique, for scattering angles from 20°to 110°. The relative DCSs were measured as a function of both the angle and incident energy and the absolute DCSs were determined using the relative flow method. The calculations of electron interaction cross sections are based on a corrected form of the independent-atom method, known as the screen corrected additivity rule procedure and using an improved quasifree absorption model. Calculated results agree very well with the experiment.

Elastic electron scattering from the DNA bases cytosine and thymine

“…The exact location of this feature appears to be correlated with electron energy. At higher [12] (dashed line) and experimental data for pyrimidine [11] (squares) where available. The statistical error in the present experimental data is less than 10% in most cases.…”

“…In its original form, we found an inherent contradiction between the ICSs derived from these two approaches, which suggested the optical theorem was being violated [11] by the first procedure. This problem was solved by employing a normalization procedure during the computation of the DCSs so that the ICSs derived from the two approaches were now entirely consistent [11]. Because no molecular structure is considered in the AR, it is only applicable when the incident electrons are fast enough that they effectively observe the target molecule as a sum of the individual atoms (typically well above 100 eV for the present sized molecules).…”

“…Alternatively, ICSs also can be derived from the relevant atomic ICSs in conjunction with the optical theorem [19]. In its original form, we found an inherent contradiction between the ICSs derived from these two approaches, which suggested the optical theorem was being violated [11] by the first procedure. This problem was solved by employing a normalization procedure during the computation of the DCSs so that the ICSs derived from the two approaches were now entirely consistent [11].…”

“…The statistical error in the data is less than 10% in most situations. Also included in the figure are calculations performed using the SCAR and IAM theoretical models and previous experimental data for pyrimidine [11].…”

“…Only recently have measurements appeared concerning more complex biological molecules, such as formic acid [7], variations of the tetrahydrofuran ring [8,9], alanine [10], and pyrimidine [11]. Because of the experimental challenges associated with producing vapor targets of these molecules, theoretical calculations tend to precede experimental investigation.…”