Abstract Based on the prior work of Chahl and Gopalakrishnan (2019) to infer particle-ion collision time distributions using a Langevin Dynamics (LD) approach, we develop a model for the non-dimensional particle-ion diffusion charging collision kernel β i or H that is applicable for 0 ≤ Ψ E ≤ 60 , 0 ≤ Ψ I Ψ E ≤ 1 , K n D ≤ 2000 (defined in the main text). The developed model for β i for attractive Coulomb and image potential interactions, along with the model for β i for repulsive Coulomb and image potential interactions from Gopalakrishnan, Thajudeen, Ouyang, and Hogan (2013b), is tested against published diffusion charging experimental data. Current state of the art charging models, Fuchs (1963) and Wiedensohler (1988) regression for bipolar charging, are also evaluated and discussed. Comparisons reveal that the LD-based model accurately describes unipolar fractions for 10 – 100 n m particles measured in air (Adachi, Kousaka, & Okuyama, 1985), nitrogen and argon but not in helium (Adachi, Okuyama, Kousaka, Kozuru, & Pui, 1987). Fuchs model and the LD-based model yield similar predictions in the experimental conditions considered, except in helium. In the case of bipolar charging, the LD-based model captures the experimental trends quantitatively (within ± 20 % ) across the entire size range of 4 – 40 n m producing superior agreement than Wiedensohler's regression. The latter systematically underpredicts charge fraction below ~ 20 n m in air (by up to 40%) for the data presented in Adachi et al. (1985). Comparison with the data of Gopalakrishnan, McMurry, and Hogan (2015), obtained in UHP air along with measurements of the entire ion mass-mobility distribution, shows excellent agreement with the predictions of the LD-based model. This demonstrates the capability to accommodate arbitrary ion populations in any background gas, when such data is available. Wiedensohler's regression, derived for bipolar charging in air using average ion mass-mobility, also describes the data reasonably well in the conditions examined. However, both models failed to capture the fraction of singly and doubly charged particles in carbon dioxide warranting further investigation.

中文翻译：

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基于朗之万动力学的扩散充电碰撞核模型的预测与经典实验的比较

摘要 基于 Chahl 和 Gopalakrishnan (2019) 使用朗之万动力学 (LD) 方法推断粒子 - 离子碰撞时间分布的先前工作，我们开发了无量纲粒子 - 离子扩散充电碰撞核 β i 或 H 的模型适用于 0 ≤ Ψ E ≤ 60 , 0 ≤ Ψ I Ψ E ≤ 1 , K n D ≤ 2000（在正文中定义）。Gopalakrishnan、Thajudeen、Ouyang 和 Hogan (2013b) 开发的用于吸引库仑和图像势相互作用的 β i 模型，以及用于排斥库仑和图像势相互作用的 β i 模型，都针对已发表的扩散充电实验数据进行了测试。还评估和讨论了当前最先进的充电模型，Fuchs (1963) 和 Wiedensohler (1988) 用于双极充电的回归。比较表明，基于 LD 的模型准确地描述了在空气 (Adachi, Kousaka, & Okuyama, 1985)、氮气和氩气中测量的 10 – 100 nm 粒子的单极分数，但不能在氦气中 (Adachi, Okuyama, Kousaka, Kozuru, & Pui) , 1987)。Fuchs 模型和基于 LD 的模型在所考虑的实验条件下产生类似的预测，但氦除外。在双极充电的情况下，基于 LD 的模型在 4 – 40 nm 的整个尺寸范围内定量捕获实验趋势（在 ± 20 % 内），产生比 Wiedensohler 回归更好的一致性。对于 Adachi 等人提供的数据，后者系统地低估了空气中低于 20 nm 的电荷分数（高达 40%）。(1985)。与 Gopalakrishnan、McMurry 和 Hogan (2015) 的数据进行比较，在 UHP 空气中获得的结果以及整个离子质量迁移率分布的测量结果与基于 LD 的模型的预测非常吻合。这表明当此类数据可用时，能够在任何背景气体中容纳任意离子群。Wiedensohler 的回归，使用平均离子质量迁移率导出空气中的双极充电，也很好地描述了所检查条件下的数据。然而，这两种模型都未能捕获二氧化碳中带单电荷和双电荷粒子的分数，值得进一步研究。s 回归，使用平均离子质量迁移率导出空气中的双极充电，也很好地描述了在检查条件下的数据。然而，这两种模型都未能捕获二氧化碳中带单电荷和双电荷粒子的分数，值得进一步研究。s 回归，使用平均离子质量迁移率导出空气中的双极充电，也很好地描述了在检查条件下的数据。然而，这两种模型都未能捕获二氧化碳中带单电荷和双电荷粒子的分数，值得进一步研究。