This study concerns the importance of the precursor (or pre-reactive) state of elementary physicochemical processes whose basic features, as structure, stability, and trapping effect of reagents, are controlled by the balance of intermolecular forces that arise at long range and operate at intermediate and short separation distances. The detailed formulation of such forces, determining formation probability and dynamical evolution of the precursor state, is of relevance in molecular science and difficult to be treated by quantum chemistry. Such a problem has been tackled by us exploiting the phenomenological approach, which employs semi-empirical and empirical formulas to represent strength, range and angular dependence of the leading interaction components involved. In addition to the study of transport phenomena, part of the attention is addressed to chemi-ionization (or Penning ionization) reactions for which neutral reagents lead to atomic and/or molecular ions plus electrons as products. Chemi-ionizations are bimolecular processes occurring in several environments of interest, where a reagent is a species, formed in excited-metastable electronic states by collisions with energetic electrons or cosmic rays. For such reactions all crucial electronic rearrangements, affecting stability and evolution of the weakly bound precursor state, here coincident with the reaction transition state, are characterized with a high detail. The results of the present study are of interest for many other processes, whose precursor states and their relevant features are difficult to characterize, often masked by several other effects.

Graphical abstract

中文翻译：

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分子间相互作用和基本物理化学过程的弱结合前体态

这项研究涉及基本物理化学过程的前体（或预反应）状态的重要性，其基本特征，如试剂的结构、稳定性和捕获效应，是由长距离产生的分子间力的平衡控制的，并在中间隔距离和短间隔距离。这种力的详细表述，决定了前体态的形成概率和动态演化，与分子科学相关，并且难以通过量子化学来处理。我们利用现象学方法解决了这个问题，该方法采用半经验和经验公式来表示所涉及的主要相互作用分量的强度、范围和角度依赖性。除了输运现象的研究之外，部分注意力还集中在化学电离（或潘宁电离）反应上，其中中性试剂产生原子和/或分子离子加上电子作为产物。化学电离是在几种感兴趣的环境中发生的双分子过程，其中试剂是一种物质，通过与高能电子或宇宙射线碰撞而形成激发亚稳态电子状态。对于此类反应，影响弱结合前体态（此处与反应过渡态一致）的稳定性和演化的所有关键电子重排均具有高度细节特征。本研究的结果对于许多其他过程也很有意义，这些过程的前体状态及其相关特征很难表征，通常被其他几种效应所掩盖。

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