Further Measurements of Thermal Energy Charge Transfer in Support of Ground-Based Astronomy

奖项编号：AST-0606960PI: Daniel savin机构：哥伦比亚大学标题：支持地面天文学的热能电荷转移的进一步测量摘要这项研究是正在进行的天体物理学兴趣的原子和离子之间热能电荷转移的实验室研究的延续。人们早就知道，热能电荷转移在确定一系列宇宙等离子体的电离结构、热结构、发射光谱和吸收光谱方面起着重要作用。这些包括在行星状星云、H区、沃尔夫-拉叶星云、明亮的蓝色可变星云、莱曼α云和星系间介质中发现的光电离气体；超新星残骸和赫比格-哈罗天体中的激波；以及原星系和第一颗恒星形成时期的原始气体云。不幸的是，在过去的25年里，为了满足对可靠的热能电荷传递数据的需求，许多理论计算的可靠性只有3-10倍。虽然最新的最先进的计算预计会更可靠，但这种努力不太常见，在不以实验为基准的情况下，误差仍可能达到3倍。然而，尽管来自社区的需求，很少有实验室测量存在。为了满足这一需求，将继续使用橡树岭国家实验室离子原子束装置对热能电荷转移进行一系列实验室测量。在这里，将测量C2+， O+, O2+， Se3+和Kr2+的热能电荷转移。在模拟行星状星云和HII区域以及超新星残骸和赫比格-哈罗天体的冲击时，需要可靠的C2+、O+和O2+的电荷转移数据。为了研究行星状星云祖先恒星中通过慢中子捕获过程进行核合成和对流吸收，需要se3 +和Kr2+的数据来分析行星状星云光谱。这些结果将用于产生速率系数，估计精度为* 20%，并将为等离子体建模提供拟合。现代电荷转移理论也将以这些结果为基准。最后，对实验装置进行改进，使其能够测量和控制离子束中的亚稳部分。对于具有显著亚稳分数的光束，这将允许提取光束中基态和亚稳离子的绝对横截面。这种新的能力将进一步增加橡树岭国家实验室离子原子合并光束装置的独特性。研究生的培训和专业准备将得到支持。该学生将完成大部分项目，部分完成哲学博士学位的要求。这项研究的结果将通过研讨会和座谈会呈现给学术界、政府和工业界的同事。在国家和国际会议上的报告将在适当的期刊上发表。此外，这项工作将进一步加强哥伦比亚/橡树岭国家实验室的研究和教育基础设施。肯塔基大学的Gary Ferlandat教授将把新的速率系数输入到CLOUDY中，CLOUDY是模拟光电离气体最常用的代码之一。

AWARD NO: AST-0606960PI: Daniel SavinINSTITUTION: Columbia UniversityTITLE: Further Measurements of Thermal Energy ChargeTransfer in Support of Ground-Based AstronomyABSTRACTThis research is a continuation of an ongoing laboratory study of thermal energycharge transfer among atoms and ions of astrophysical interest. It has long been knownthat thermal energy charge transfer plays an important role in determining the ionizationstructure, thermal structure, emission spectrum and absorption spectrum for a range ofcosmic plasmas. These include photoionized gas found in planetary nebulae, H II regions,Wolf-Rayet nebulae, luminous blue variable nebulae, Lyman alpha clouds, and theintergalactic medium; shocks in supernova remnants and Herbig-Haro objects; andprimordial gas clouds during the epoch of protogalaxy and first star formation.Unfortunately, many theoretical calculations carried out during the past 25 years inresponse to the demand for reliable thermal energy charge transfer data are reliable toonly a factor of 3-10. And while the latest state-of-the-art calculations are expected to bemore reliable, such efforts are less common and can still be off by a factor of 3 when notbenchmarked against experiments. However, few laboratory measurements exist despitethe demand from the community.To address this need, an ongoing series of laboratory measurements of thermal energycharge transfer will be continued using the Oak Ridge National Laboratory ion-atommerged-beams apparatus. Here, measurements will be made of the thermal energy chargetransfer of C2+, O+, O2+, Se3+, and Kr2+. Reliable charge transfer data for thecosmically abundant C2+, O+, and O2+ are needed for modeling planetary nebulae and HII regions as well as shocks in supernovae remnants and Herbig-Harrow objects. Data forSe3+ and Kr2+ are needed to analyze planetary nebula spectra in order to study bothnucleosynthesis via the slow neutron capture process and convective dredge-up in theplanetary nebula progenitor stars. These results will be used to produce rate coefficientswith an estimated accuracy of * 20% and will provide fits for plasma modeling. Moderncharge transfer theory will also be benchmarked against these results. Finally, thelaboratory apparatus will be modified so that the metastable fraction in the ion beams canbe measured and controlled. For beams with a significant metastable fraction, this willallow the extraction of absolute cross sections for both the ground state and metastableions in the beam. This new capability will further increase the uniqueness of the OakRidge National Laboratory ion-atom merged-beams apparatus.The training and professional preparation of a graduate student will be supported. Thisstudent will carry out a large portion of the project in partial fulfillment of therequirements for the degree of Doctor of Philosophy. The results of this research will bepresented via seminars and colloquia to colleagues in academia, government, andindustry. Reports at national and international conferences will be given and published inthe appropriate journals. In addition, this work will further enhance the Columbia/OakRidge National Laboratory infrastructure for research and education. Prof. Gary Ferlandat the University of Kentucky will input the new rate coefficients into CLOUDY which isone of the most commonly used codes for modeling photoionized gas.