Collaborative Research: Improving and calibrating a Tunable Infrared Laser Direct Absorption Spectroscopy (TILDAS) system for clumped isotope analysis of CO2

对“聚集同位素”的研究关注的是重同位素之间相互“聚集”成键的趋势，而不是天然物质中的轻同位素，这种趋势取决于温度。两种稀有且质量更大的碳和氧同位素聚集在二氧化碳中的同时出现，包含了涉及这些分子的最新化学反应温度的信息。聚集同位素地球化学已被应用于广泛的主题-从限制大气二氧化碳预算到陨石的温度历史。CO2聚集的测量使重建热液系统，气候历史，古海拔和上地壳冷却历史的新进展。这种方法没有得到更广泛的实践的主要原因是测量的困难。该奖项将提供一种新的基于激光的仪器，用于测量碳酸盐中的聚集同位素，该仪器比现有的质谱仪系统更快，更便宜，并且需要更少的样品材料。这种新仪器将完全改变聚集同位素研究的格局，使其成为一种普通的分析。这样的系统将很快被世界各地的实验室采用，用于地质、海洋、生物和大气样品，从而为许多科学学科带来新的研究可能性。该项目还扩大了地球化学这一不寻常的分支学科的培训和教育机会。该项目将支持博士后研究人员，加强国际合作，并通过激光方法会议传播成果。该项目还将整合研究和教育，扩大代表性不足的群体的参与，并通过支持STEM Futures Fellowship研究经验，为那些认同历史上代表性不足的地球科学群体的本科生广泛传播成果。该项目建立在我们以前资助的工作基础上，开发了一种基于激光的工作（可调谐红外激光直接吸收光谱- TILDAS）仪器，用于快速精确测量CO2的聚集同位素（例如，13C18O16O）。基本仪器已经建成，但需要进一步改进稳定性和开发实际样品处理，以生产出可在科学界广泛使用的仪器。与目前使用的质谱法相比，这种基于激光的测量方法具有更快的速度，只需20分钟的分析就可以达到所需的精度。小样本量（相当于最小的质谱仪系统，并有可能进一步减少）和大幅增加的吞吐量将允许地球化学家提取以前无法获得详细的温度信息从精细分层档案，如贝壳，鱼耳石，洞穴沉积物，土壤碳酸盐，凝灰岩和碳酸盐岩。精细取样还将使研究人员能够更有效地剖析碳酸盐岩的成岩历史，解决与固态重新排序有关的问题，研究在地下沉淀的分区岩石再填充水泥，并研究动力学和生命效应。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

The study of “clumped-isotopes” concerns the tendency of heavy isotopes to “clump” into bonds with each other rather than with light isotopes in natural materials, a tendency that is temperature dependent. The co-occurrence of two rare and more massive isotopes of carbon and oxygen clumped in CO2 holds information on the temperature of the most recent chemical reactions involving these molecules. Clumped-isotope geochemistry has been applied to a wide range of subjects – from constraining atmospheric CO2 budgets to the temperature histories of meteorites. Measurements of clumping in CO2 have enabled new advances in reconstructing hydrothermal systems, climate history, paleoelevation, and the cooling history of the upper crust. The primary reason that this methodology is not more widely practiced is the difficulty of the measurement. This award will deliver a new laser-based instrument for measurement of clumped isotopes in carbonates that is much faster, cheaper, and requires less sample material than existing mass spectrometer systems. This new instrument will completely alter the landscape for clumped isotope research, making it a commonplace analysis. Such a system would be adopted quickly by laboratories around the world for application to geologic, oceanographic, biologic, and atmospheric samples, leading to new research possibilities in many scientific disciplines. This project also expands training and educational opportunities in this unusual sub-discipline of geochemistry. This project will support a postdoctoral researcher, strengthen international collaborations, and disseminate results through a conference session on laser methods. The project will also integrate research and education, broaden the participation of underrepresented groups, and broadly disseminate results by supporting a STEM Futures Fellowship research experience for undergraduates who identify with historically underrepresented groups in geoscience. This project builds on our previous funded work to develop a working laser-based (Tunable Infrared Laser Direct Absorption Spectroscopy - TILDAS) instrument for the rapid and precise measurement of clumped isotopologues of CO2 (e.g., 13C18O16O). The basic instrument has been constructed, but additional improvements in stability and development of practical sample processing are needed to produce an instrument that can be used widely in the scientific community. This laser-based measurement has major advantages over the currently used mass spectrometry approach in that it is much faster, taking only 20 minutes of analysis to achieve the required precision. Small sample size (comparable to the smallest mass spectrometer systems, and with the potential for further reductions) and a major increase in through-put will allow geochemists to extract previously unobtainable detailed temperature information from finely layered archives such as shell, fish otoliths, speleothems, soil carbonates, tufas and travertines. Fine sampling will also allow researchers to more effectively dissect diagenetic histories in carbonates, address questions related to solid-state reordering, study zoned fracture-filling cements precipitated in the sub-surface, and study kinetic and vital effects.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.