Institute of Fine Chemical Technologies named after M.V. Lomonosov, Russian Technological University-MIREA, Prosp. Vernadskogo 86, 119571 Moscow, Russian Federation.
Research Computing Center, Lomonosov Moscow State University, 119899 Moscow, Russian Federation.
J Chem Phys. 2019 Feb 7;150(5):054201. doi: 10.1063/1.5060673.
The development of electron sources capable of temporal resolution on the order of 1 ps or less raises a number of questions associated with the estimation of the physical meaning and accuracy of the dynamic parameters based on the analysis of time-dependent scattering intensity. The use of low brightness ultrashort pulses with few electrons leads to the necessity for increasing the total exposure time and lengthening the time of data acquisition, with attendant problems with the limited sample. The sample restrictions can be mitigated by increasing the charge per pulse, i.e., by going to high brightness sources. Increasing in the number of electrons, however, is limited by the Coulomb repulsion between them, which leads on one hand to distortion of the diffraction pattern and on the other hand to an increase in the duration of the pulse. An analytical technique for estimating the deformation of the diffraction pattern caused by the Coulomb repulsion of the electrons in electron bunches with duration of less than 10 ps and the influence of this effect on the accuracy of determination of the interatomic distances is developed for the non-relativistic and relativistic regimes for electron energies.
能够在 1 ps 或更短的时间内实现时间分辨率的电子源的发展提出了许多问题，这些问题与基于分析随时间变化的散射强度来估计物理意义和动态参数的准确性有关。使用具有少量电子的低亮度超短脉冲会导致需要增加总曝光时间并延长数据采集时间，从而导致对有限样本的限制。通过增加每个脉冲的电荷量，即通过使用高亮度源，可以减轻样本限制。然而，电子数量的增加受到它们之间的库仑斥力的限制，这一方面导致衍射图案的变形，另一方面导致脉冲持续时间的增加。为了非相对论和相对论两种电子能量情况，开发了一种分析技术，用于估计持续时间小于 10 ps 的电子束中电子的库仑斥力引起的衍射图案变形及其对确定原子间距离的准确性的影响。
