Laboratory Measurements of Dissociative Recombination with Cold Molecular Ions for Ground-Based Studies of Diffuse Molecular Clouds

在弥散星际介质中，分子离子与电子的解离复合是分子离子被破坏的主要过程。这项研究项目将测定三个分子离子CF+、CH+和SH+在实验室模拟太空条件下的低温和压力下的DR反应速率。这项研究的速率将使天文学家能够推断出这些离子的准确丰度，并将它们用作星际气体的物理和化学探测器。该项目将支持博士后学者的培训，并为本科生提供研究机会。研究团队将使用位于德国海德堡马克斯·普朗克核物理研究所的低温存储环(CSR)进行实验室DR测量。CSR可以存储离子超过1000秒，使它们能够以辐射方式冷却到与扩散分子云中的离子相当的低旋转能级。利用DR测量，该团队将在与漫射云相关的低温下产生准确的热速率系数。来自该项目的可靠的DR数据将使天文学家能够使用CF+、CH+和SH+丰度来探测扩散气体中的关键性质和过程。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Dissociative recombination (DR) with electrons is the dominant process by which molecular ions are destroyed in the diffuse interstellar medium. This research project will determine the rates of DR reactions of three molecular ions CF+, CH+, and SH+ in the laboratory at low temperatures and pressures that simulate the conditions in space. Rates from the study will allow astronomers to infer accurate abundances of these ions and use them as probes of the physics and chemistry of the interstellar gas. The project will support the training of a postdoctoral scholar and provide research opportunities to an undergraduate student.The research team will perform the laboratory DR measurements using the Cryogenic Storage Ring (CSR) located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. The CSR can store ions for over 1,000 seconds, allowing them to cool radiatively to low rotational energy levels comparable to those in diffuse molecular clouds. Using the DR measurements, the team will generate accurate thermal rate coefficients at low temperatures relevant to diffuse clouds. Reliable DR data from the project will enable astronomers to use CF+, CH+, and SH+ abundances to probe key properties and processes in the diffuse gas.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.