The model-potential approach previously developed by the authors to study positron interactions with molecules is used to calculate the positron binding energy for n-alkanes (C_nH_2n+2) and the corresponding cycloalkanes (C_nH_2n). For n-alkanes, the dependence of the binding energy on the conformation of the molecule is investigated, with more compact structures showing greater binding energies. As a result, thermally averaged binding energies for larger alkanes (n ≳ 9) show a strong temperature dependence in the range of 100 K–600 K. This suggests that positron resonant annihilation can be used as a probe of rotational (trans-gauche) isomerization of n-alkanes. In particular, the presence of different conformers leads to shifts and broadening of vibrational Feshbach resonances in the annihilation rate, as observed with a trap-based low-energy positron beam.

中文翻译：

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分子组成和构象对烷烃中正电子结合和an灭的影响

先前由作者与分子研究正电子相互作用开发的模型，可能的方法是用于计算正电子结合能为ñ -烷烃（C _ñ ħ _{2 Ñ 2}）和相应的环烷烃（C _ñ ħ _{2 Ñ}）。对于正构烷烃，研究了结合能对分子构象的依赖性，其中更紧密的结构显示出更大的结合能。结果，较大烷烃（n = 9）的平均热键能在100 K–600 K范围内显示出强烈的温度依赖性。这表明正电子共振an灭可用作旋转探针（正构烷烃的反式gauche）异构化。特别地，如基于阱的低能正电子束所观察到的，存在不同的构象异构体会导致F灭率中的振动Feshbach共振移动和变宽。