气相中碰撞后热激发与受存活限制的团簇生长
Post-Collision Thermal Excitation and Survival-Limited Cluster Growth in the Gas Phase
浏览论文内容
中文总结 AI 辅助
该研究针对气相团簇生长的传统等温模型不足，开发了受存活限制的热激发框架，结合模拟验证后发现存活概率具非单调尺寸依赖，修正后可大幅改变生长时间，为团簇生长控制提供通用途径。
中文摘要 AI 辅助
通过单体添加实现的气相团簇生长通常被建模为等温过程。我们开发了一种受存活限制的框架，其中缔合过程会产生热激发团簇，该团簇可能在通过浴气碰撞冷却或遇到下一个单体之前发生解离。我们首先针对单个缔合后的热轨迹推导了连续能量存活概率，随后利用轨迹泛函对激发能、平衡能和单体到达时间的分布进行了边际化处理。对水团簇、银团簇和金团簇的分子动力学模拟提供了与尺寸相关的热容关系和潜热，而基于事件的蒙特卡洛模拟则独立验证了该存活公式。理论与蒙特卡洛结果吻合度极高。系综平均存活概率呈现出强烈且非单调的尺寸依赖性，其中最小团簇通常面临最大的热惩罚。仅当保留完整的团簇能量分布时才会出现中等尺寸的局部最大值，这源于曲率增强的解离效应与低能尾随尺寸增加而变窄之间的竞争。因此，存活的团簇优先来自碰撞前能量分布的较冷部分，而平均热轨迹可能会大幅低估种群存活概率。为了将单事件存活与累积生长关联起来，我们引入了相对于等温参考的热正向速率修正，并将其纳入可逆生灭模型中。尽管每个尺寸对应的修正值可能较为温和，但其累积效应可使平均首次通过时间提高多个数量级。该框架为识别碰撞后稳定化作为气相团簇生长的控制因素提供了通用途径。
英文摘要
Gas-phase cluster growth by monomer addition is commonly modeled as an isothermal process. We develop a survival-limited framework in which association produces a thermally excited cluster that may dissociate before either cooling through bath-gas collisions or encountering the next monomer. A continuous-energy survival probability is first derived for an individual post-association thermal trajectory and is then marginalized over distributions of excitation energy, equilibrium energy, and monomer-arrival time using a trajectory functional. Molecular-dynamics simulations of water, silver, and gold clusters provide size-dependent caloric relationships and latent heats, while event-based Monte Carlo simulations independently test the survival formulation. Theory and Monte Carlo results agree closely. The ensemble-averaged survival probability exhibits strong and non-monotonic size dependence, with the largest thermal penalties generally occurring for the smallest clusters. Intermediate-size local maxima arise only when complete cluster-energy distributions are retained and result from competition between curvature-enhanced dissociation and the narrowing of the low-energy tail with increasing size. Surviving clusters are consequently drawn preferentially from the colder portion of the pre-collision energy distribution, and mean thermal trajectories can substantially underestimate population survival. To connect single-event survival to cumulative growth, we introduce a thermal forward-rate correction relative to an isothermal reference and incorporate it into a reversible birth--death model. Although the correction at each size may be moderate, its multiplicative accumulation can increase mean first-passage times by many orders of magnitude. The framework provides a general route for identifying post-collision stabilization as a control on gas-phase cluster growth.
