Collision-induced few-body dynamics of atomic and molecular systems

原子和分子是量子世界的对象。考虑到量子力学的基本定律自20世纪20年代以来就已为人所知，人们可能会认为原子和分子的结构和动力学现在已经被很好地理解，并且可以使用这些定律计算到任何所需的精度水平。事实并非如此。当涉及到动力学时，除了最简单的情况之外，已知方程的精确解是不可行的，并且尽管计算资源的可用性不断增加，但在未来一段时间内它们也是不可行的。问题的核心在于量子力学少体问题的复杂性，从根本上讲，正是对这个问题的兴趣推动了这项研究计划。我们将通过研究离子与原子和分子的碰撞，并求解控制碰撞相互作用的基本方程的简化版本来研究量子少体动力学。这些简化的方程仍然很复杂，无法用笔和纸的形式来求解。因此，我们将开发算法和计算机程序来获得数值解。将它们与实验数据进行比较将揭示量子动力学的作用以及我们方法的有用性和局限性，从而促进我们对量子力学少体问题的理解。我们的研究也将有利于在这一领域工作的实验人员。他们将帮助他们解释他们的数据，并指导他们设计未来的实验。例如，最近锂原子的电离测量提出了一个问题，即涉及三个锂电子中的两个的某些过程是否有助于测量光谱。我们计划研究这些过程的作用和性质。我们的计算将解决的一个问题是，它们是否由撞击离子与每个电子的独立相互作用主导，或者电子之间的相互作用是否也很重要。后一种相互作用与所谓的电子关联效应有关，电子关联效应在许多原子、分子和凝聚态系统中起着核心作用，并引起超导性等有趣现象，我们的工作也将有重要的应用。这项研究计划的一个主要目标是推动我们的方法，使其适用于涉及有机分子的碰撞。这将与放射生物学领域有关。当生物组织被质子或重离子照射时，电子被释放，电离的分子可能会分裂。在肿瘤放射治疗中，这有助于肿瘤的期望破坏和周围组织的不期望破坏。要从根本上了解辐射损害问题，就需要详细分析潜在的碰撞过程。这就是我们的研究所关注的。从长远来看，它将有利于对大分子（如DNA碱基）的复杂损伤领域，并可能产生一些社会影响，因为它的结果可能有助于更成功地治疗癌症。

Atoms and molecules are objects of the quantum world. Given that the basic laws of quantum mechanics have been known since the 1920s, one might think that atomic and molecular structure and dynamics are well understood by now and can be calculated, using those laws, to any desired level of accuracy. This is not the case. When it comes to dynamics, exact solutions of the known equations are not feasible, except for the simplest situations, and they will not be feasible for some time to come despite the ever-increasing availability of computational resources. At the heart of the matter lies the complexity of the quantum-mechanical few-body problem, and on a fundamental level, it is the interest in this problem that drives this research program. We will study quantal few-body dynamics by looking into collisions of ions with atoms and molecules and solving simplified versions of the fundamental equations that govern the collisional interactions. These simplified equations are still far to complex to be solved in pen and paper form. Accordingly, we will develop algorithms and computer programs to obtain numerical solutions. Comparing them with experimental data will shed light on the quantum dynamics at play and on the usefulness and the limitations of our methods, thereby advancing our understanding of the quantum-mechanical few-body problem. Our studies will also benefit the experimentalists working in this area. They will assist them in interpreting their data and guide them in the design of future experiments. For example, recent ionization measurements of lithium atoms have raised the question whether certain processes which involve two of the three lithium electrons contribute to the measured spectra. We plan to study the role and the nature of these processes. One question our calculations will address is whether they are dominated by independent interactions of the impinging ion with each electron, or if the interaction between the electrons is important as well. The latter interaction is associated with so-called electron-correlation effects, which play a central role in many atomic, molecular and condensed-matter systems and give rise to such interesting phenomena as superconductivity.Our work will also have significant applications. A major goal of this research program is to push our methods to make them applicable to collisions involving organic molecules. This will be relevant for the field of radiobiology. When biological tissue is irradiated by protons or heavy ions, electrons are set free and the ionized molecules may break apart. In tumour radiation therapy this contributes to the desired destruction of the tumour and to the undesired destruction of the surrounding tissue. Understanding the problem of radiation damage on a fundamental level requires the detailed analysis of the underlying collision processes. This is what our research is concerned with. In the long term it will benefit the complex field of damage to large molecules such as DNA bases and will potentially have some societal impact in that its outcomes may contribute to a more successful treatment of cancer.