发表机构
Università di Trento; Synchrotron SOLEIL; Universidad Autonoma de Madrid; Universidad de Salamanca（特伦托大学; 索莱尔同步辐射中心; 马德里自治大学; 萨拉曼卡大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过实验与理论结合，研究了P$^+$与C$_2$H$_2$的反应，发现其主要生成HCCP$^+$（分支比99%），并修订了天体化学速率系数，为太空中磷物种形成提供了新途径。
AI 中文摘要
尽管磷在宇宙中的丰度较低，但它是一种生物必需元素，其前生物可利用性及其在生物分子中的掺入仍是悬而未决的问题。在天文环境中，目前仅检测到少数含P-C键的含磷分子（如CP、CCP、HCP）。已有研究提出了更复杂的物种，但其形成和破坏途径仍缺乏约束。涉及P阳离子的气相离子-分子化学可能有助于有机磷的形成，特别是在原恒星激波和外流中，而基态P阳离子与闭壳层中性分子的反应则为自旋禁阻机制提供了基准。我们通过实验与理论相结合的研究，探讨了P$^+$与C$_2$H$_2$的反应，旨在修订天体化学数据库中的速率系数。我们测量了作为碰撞能函数的绝对截面和分支比，并通过高精度电子结构计算以及考虑高阶长程相互作用和中间复合物形成的精细捕获模型进行了补充。在10至5000 K的温度范围内推导了各通道的速率系数。该反应主要生成HCCP$^+$ + H（分支比为99%），而CCP$^+$ + H$_2$是次要通道（分支比为1%），该通道源于从三重态到单重态势能面的系间窜越。300 K时的总速率系数与SIFT值吻合良好，但随温度降低而增大，偏离了纯Langevin趋势。该反应应纳入磷以P$^+$形式释放的天体化学模型中，例如激波中冰粒的剧烈加工过程。它为线性HCCP$^+$提供了一条生成途径，而HCCP$^+$可能是通过解离重组生成观测到的CP和CCP物种的相关前体。
英文摘要
Despite its low cosmic abundance, phosphorus is a bioessential element whose prebiotic availability and incorporation into biomolecules remain open questions. Only a few phosphorous containing molecules with P to C bonds have been detected in astronomical environments (CP, CCP, HCP). More complex species have been proposed, but their formation and destruction pathways remain poorly constrained. Gas-phase ion molecule chemistry involving P cations may contribute to organophosphorus formation, particularly in protostellar shocks and outflows, while reactions of ground state P cations with closed-shell neutrals provide benchmarks for spin-forbidden mechanisms. We investigate the reaction of P+ with C$_2$H$_2$ through a joint experimental and theoretical study aimed at revising astrochemical database rate coefficients. Absolute cross sections and branching ratios were measured as a function of collision energy and complemented by high-level electronic structure calculations and a refined capture model accounting for higher-order long-range interactions and intermediate complex formation. Channel-specific rate coefficients were derived in the range from 10 to 5000 K. The reaction produces predominantly HCCP$^+$ + H (branching ratio 99%), while CCP$^+$ + H$_2$ is a minor channel (branching ratio 1%) arising from intersystem crossing from the triplet to the singlet potential energy surfaces. The total rate coefficient at 300 K agrees well with the SIFT value, but it increases with decreasing temperature, deviating from a pure Langevin trend. The reaction should be included in astrochemical models where phosphorus is released as P+, such as during energetic processing of icy grains in shocks. It provides a pathway to linear HCCP$^+$, a potentially relevant precursor to the observed CP and CCP species through dissociative recombination
Comments22 pages, 6 figures, 1 Appendix, submitted to A&A
