Laboratory measurements of three deuterium substitution reactions important in interstellar chemistry

占据星际空间（恒星之间的空间）的极冷和稀薄的气体和尘埃云拥有丰富的化学物质。 该研究项目将研究最简单的多原子分子离子的化学反应，这些离子驱动星际气体的化学反应。 这些离子可以在极低的温度下存在，而大多数其他分子在这种温度下会冻结。 研究小组将使用一个复杂的实验室实验来准确地确定离子在非常低的温度下的反应速率。 这项研究的结果将使天文学家能够更好地了解这些离子在太空中的丰度，并将它们用作星际云内最冷和最密集区域的探测器，这些区域是恒星和行星的诞生地。 该项目将有助于博士后学者的培训和专业发展。 该项目还将支持一项对初中和高中科学教育产生积极影响的计划。研究小组将对原子氘与H3+（星际气体中最简单的多原子离子）及其氘代形式H2 D+和D2 H+的气相反应进行实验室研究。 这三个反应在化学反应中非常重要，大大增加了星际分子的氘含量; H2 D+和D2 H+离子探测了冷乌云的致密区域，大多数其他分子在那里冻结。 因此，了解这些离子的化学性质对于了解这些区域至关重要，这些区域是星星和行星形成的潜在场所。 这些研究具有挑战性，因为原子和分子离子很难在实验室中产生。 该团队将使用双源合并快速束装置测量D原子与H3+，H2 D+和D2 H+反应的速率系数，该装置是在先前NSF支持下建造的（AST-0905832），使他们能够产生和反应原子和分子离子束。 从测得的速率系数中提取的碰撞截面将用于生成与冷星际云（10 K - 100 K）相关的温度下的热速率系数。 预计速率系数的准确度在15%以内，比三种反应的计算结果高出一个数量级。 该项目将资助哥伦比亚大学的一名博士后学者。 该项目还将允许团队成员继续参与哥伦比亚大学暑期研究计划，该计划让初中和高中教师参与科学研究，并已被证明有助于留住学校教师，提高学生在科学课程中的表现。

The extremely cold and tenuous clouds of gas and dust that occupy interstellar space -- the space between the stars -- host a rich chemistry. This research project will study chemical reactions of the simplest polyatomic molecular ions that drive the chemistry of the interstellar gas. These ions can exist at the very low temperatures at which most other molecules freeze out. The research team will use a sophisticated laboratory experiment to accurately determine reaction rates of the ions at very low temperatures. Results from the study will allow astronomers to better understand the abundance of these ions in space and to use them as probes of the coldest and densest regions within interstellar clouds, which are birthplaces of stars and planets. The project will contribute to the training and professional development of a postdoctoral scholar. The project will also support a program that is known to have a positive impact on middle school and high school science education.The research team will perform laboratory studies of the gas-phase reactions of atomic deuterium with H3+ -- the simplest polyatomic ion found in the interstellar gas -- and its deuterated forms H2D+ and D2H+. The three reactions are important in the chemistry that drastically increases the deuterium content of interstellar molecules; and the H2D+ and D2H+ ions probe the densest regions of cold dark clouds where most other molecules freeze out. Understanding the chemistry of these ions is therefore essential to understanding these regions, which are potential sites of star and planet formation. The proposed studies are challenging because atoms and molecular ions are difficult to produce in the laboratory. The team will measure rate coefficients of the reactions of D atoms with H3+, H2D+, and D2H+ using a dual-source, merged fast-beams apparatus, which was built with prior NSF support (AST-0905832), that enables them to produce and react beams of atoms and molecular ions. Collisional cross sections extracted from the measured rate coefficients will be used to generate thermal rate coefficients at temperatures relevant to cold interstellar clouds (10 K - 100 K). The rate coefficients are expected to be accurate to within 15% -- about an order of magnitude better than those calculated for the three reactions. The project will support a postdoctoral scholar at Columbia University. The project will also allow team members to continue participating in the Columbia University Summer Research Program that engages middle school and high school teachers in scientific research, and has been shown to help retain teachers in school and improve student performance in science courses.