近日，德国联邦物理技术研究院及其研究团队取得一项新进展。经过不懈努力，他们进行嘧啶双微分电子碰撞电离截面的对比实验与理论研究。相关研究成果已于2024年6月24日在国际知名学术期刊《物理评论A》上发表。

为了构建基于轨道结构的DNA辐射损伤模拟的全面数据集，该研究团队测量了嘧啶（核碱基胞嘧啶和胸腺嘧啶的组成部分）在30 eV至1 keV的一次电子能量范围内，其与发射角和二次电子能量的关系。测量覆盖了二次电子能量从4 eV至一次电子能量的一半，以及发射角在25°至135°的广泛范围。基于实验的双微分电离截面数据，研究人员进一步确定了嘧啶的单微分电离截面和总电离截面，并将这些结果与binary-encounter-Bethe模型的计算结果进行了比较。

除了测量之外，研究人员还开发了一种计算三重和双重微分电离截面的理论方法，该方法基于畸变波玻恩近似，分子轨道的单中心展开和T矩阵在不同分子取向上的平均。计算得到的嘧啶双微分电离截面与实验结果定性吻合较好。

附：英文原文

Title: Comparative experimental and theoretical study on doubly differential electron-impact ionization cross sections of pyrimidine

Author: M. Dinger, W. Y. Baek, H. Rabus

Issue&Volume: 2024/06/24

Abstract: To provide a comprehensive data set for track-structure-based simulations of radiation damage in DNA, doubly differential electron-impact ionization cross sections of pyrimidine, a building block of the nucleobases cytosine and thymine, were measured for primary electron energies between 30 eV and 1 keV as a function of emission angle and secondary electron energy. The measurements were performed for secondary electron energies from 4 eV to about half of the primary electron energy and for emission angles between 25° and 135°. Based on the experimental doubly differential ionization cross sections, singly differential and total ionization cross sections of pyrimidine were determined and compared to calculations using the binary-encounter-Bethe model. In addition to the measurements, a theoretical approach for calculating triply and doubly differential ionization cross sections was developed, which is based on the distorted wave Born approximation, a single center expansion of molecular orbitals, and an averaging of the T matrix over different molecular orientations. The calculated doubly differential ionization cross sections of pyrimidine show qualitatively good agreement with the experimental results.

DOI: 10.1103/PhysRevA.109.062813

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.062813