Accurate absorption models for gases at high pressure and temperature support advanced optical combustion diagnostics and aid in the study of harsh planetary atmospheres. Developing and validating absorption models for these applications requires recreating the extreme temperature and pressure conditions of these environments in static, uniform, well-known conditions in the laboratory. Here, we present the design of a new gas cell to enable reference-quality absorption spectroscopy at high pressure and temperature. The design centers on a carefully controlled quartz sample cell housed at the core of a pressurized ceramic furnace. The half-meter sample cell is relatively long compared to past high-pressure and -temperature absorption cells, and is surrounded by a molybdenum heat spreader that enables high temperature uniformity over the full length of the absorbing gas. We measure the temperature distribution of the sample gas using in situ thermocouples, and fully characterize the temperature uniformity across a full matrix of temperatures and pressures up to 1000 K and 50 bar. The results demonstrate that the new design enables highly uniform and precisely known temperature and pressure conditions across the full absorbing path length. Uniquely, we test the new gas cell with a broadband (~2500 cm⁻¹), high-resolution (0.0066 cm⁻¹) dual frequency comb spectrometer that enables highly resolved absorption spectroscopy across a wide range of temperature and pressure conditions. With this carefully characterized system, we measure the spectrum of CO₂ between 6800 and 7000 cm⁻¹ at pressures between 0.2 and 20 bar, and temperatures up to 1000 K. The measurements reveal discrepancies from spectra predicted by the HITRAN2016 database with a Voigt line shape at both low- and high-pressure conditions. These results motivate future work to expand absorption models and databases to accurately model high-pressure and -temperature spectra in combustion and planetary science research.

高压和高温气体的精确吸收模型可支持高级光学燃烧诊断，并有助于研究恶劣的行星大气。为这些应用开发和验证吸收模型需要在实验室中的静态，均匀且众所周知的条件下重新创建这些环境的极端温度和压力条件。在这里，我们介绍一种新型气室的设计，以实现在高压和高温下具有参考质量的吸收光谱。该设计的中心是一个精心控制的石英样品池，该样品池位于加压陶瓷炉的核心。与过去的高压和高温吸收池相比，半米样品池相对较长，并由钼散热器围绕，该钼散热器可在吸收气体的整个长度上实现高温均匀性。我们使用以下方法测量样气的温度分布现场热电偶，并全面表征整个温度和压力高达1000 K和50 bar的矩阵中的温度均匀性。结果表明，新设计可在整个吸收路径长度上实现高度均匀且精确已知的温度和压力条件。独特地，我们使用宽带（〜2500 cm ^-1），高分辨率（0.0066 cm ^-1）双频梳状光谱仪测试新型气室，该光谱仪能够在广泛的温度和压力条件下实现高度分辨的吸收光谱。使用这个经过精心设计的系统，我们可以测量6800至7000 cm ^-1之间的CO ₂光谱在0.2至20 bar的压力下以及高达1000 K的温度下进行的测量。这些测量结果揭示了在低压和高压条件下，HITRAN2016数据库预测的光谱具有Voigt线形的差异。这些结果激发了未来的工作，以扩展吸收模型和数据库，以精确地模拟燃烧和行星科学研究中的高压和高温光谱。