# Cryogenic System for FTIR Analysis of Hydrocarbon Fuels at Low Temperature and Atmospheric Pressure
## 1 Introduction  
Since the creation of spectroscopy direction and its technologies, allowing research materials using spectroscopic methods at low temperatures, the whole process has always been accompanied by vacuum formation. Otherwise, it would be difficult to study the nanostructure [1, 2], molecular composition [3, 4] and physical, chemical, thermal, and optical properties [5, 6, 7] of a substance due to the presence of moisture and other impurities in the ambient atmosphere that prevent high-quality research and substance analysis by any of the spectroscopic methods, including FTIR [8, 9, 10, 11].  
Low-temperature research of materials [12], including hydrocarbon compounds, which implies using IR spectroscopy, involves the presence of ultra-low pressure, i.e., vacuum. On account of this, high-quality fundamental research on the hydrocarbon substances' optical properties under atmospheric pressure is still not popular since this situation is associated with a number of problems, such as developing complexity, maintaining and further upgrading technologies for spectroscopic study that allow achieving low temperatures at atmospheric pressure, the complexity of creating an inert or IR-inactive environment [13, 14]that would help to achieve accuracy due to the low noise level of spectra and high radiation intensity, and also the lack of developed accurate step-by-step methodology of research.  
There are few technologies worldwide for studying hydrocarbon substances at low temperatures and atmospheric pressure. Although some studies [15; 16; 17; 18; 19] report spectroscopic experiments under these conditions, scientific research in this area remains limited due to the challenges mentioned earlier. We propose a technology for FTIR spectroscopy of hydrocarbon fuels at atmospheric pressure and cryogenic temperatures (80 K), offering solutions to these challenges in non-vacuum environments.  
This article presents an experimental setup: a cryogenic-capillary system with low-temperature cell and corresponding measurement technique. This system enables the acquisition of novel fundamental data on the properties and behavior of hydrocarbon materials at low temperatures and atmospheric pressure--data that can significantly advance high-quality research in this area. In particular, it provides insights into molecular behavior under these conditions, which can support the development of more accurate and efficient technological equipment. Also, this work can contribute to information replenishment as fundamental spectral data of hydrocarbons at low temperatures for overall study of extraterrestrial ices being conducted by many scientists from various space missions launched by Nasa, ESA, etc. This new device and measurement technique can be used in the engineering sphere as a new method and technology for obtaining fundamental data about the behavior of hydrocarbon compounds under specific conditions.  
Their spectra are compared with those reported by other researchers [20; 21; 22; 23; 24; 25; 26; 27; 28] to validate the performance and efficiency of the proposed technique and setup, which is the aim of this work. The results of our research and obtained spectra confirm the efficiency of our developed device.