Aromatic And Aliphatic Organic Materials In Extraterrestrial Objects Of The Solar System

Infrared spectroscopy is particularly important in the study of astrochemistry.There are various types of celestial bodies in the solar system,such as planets,satellite,comet,and asteroid which its analysis of the composition has always been one of the focuses of astronomers’research.However,we hardly knew anything about these celestial bodies for their long distance and the research method are limited.Therefore,the observation of infrared spectra of these objects is one of the more mature and systematic research methods in the study of astrochemistry.In the past decades,infrared spectroscopy can be used as an important tool for understanding the physical and chemical environment of various celestial bodies.It can help us to analyze the existence of organic material in celestial bodies and explain its formation mechanism,which can help us further understand the nature and evolutionary process of celestial bodies.In many infrared spectrum,two characteristic absorptions of 3.3μm and 3.4μm can be observed simultaneously.With respect to these two characteristic absorptions,it is currently believed that 3.3μm radiation is derived from benzene ring aromatic C-H bond vibrations,while 3.4μm radiation originates from stretching vibrations of chain aliphatic C-H bonds.Therefore,we can use the 3.3μm and 3.4μm spectral features as"tracers"for analysing the chemical structure of celestial bodies’organic material and obtain aliphatic fraction of organic substances in IR quantitative analysis.In this paper,the aliphatic fraction of organic material refers to N_C,aliph/N_C,arom（i.e The number of C atoms in aliphatic units to that in aromatic rings）or N_C-H,aliph/N_C-H,arom（i.e The number of C-H bonds in aliphatic units to that in aromatic rings）.And it can be estimated by the ratio of the intrinsic oscillator strengths A(A_3.3/A_3.4)and the ratio of the absorption intensityτ,where A_3.3is the intrinsic oscillator strength of the 3.3μm aromatic C-H streth,A_3.4 is the intrinsic oscillator strength of the 3.4μm aplihatic C-H streth.A large number of literature studies have given the value of the intrinsic oscillator strengths（per chemical bond）of the 3.3μm aromatic C-H streth of various organic molecules and the intrinsic oscillator strengths of the 3.4μm aplihatic C-H streth.On the one hand,we have optimized and obtained a more reasonable values of A_3.3/A_3.4,on the other hand,we will focus on calculating the absorption intensity of the 3.3μm and 3.4μm which we have obtained to calculate the ratio ofτ.Finally,the aliphatic fraction of the organic material in various celestial bodies is calculated.To verify the universality of this method,we selected several objects as the research object in different celestial bodies such as the comets,satellites,and meteorolite to calculate the aliphatic fraction of organic material.The results confirmed that this work has great importance to the analysis of celestial organic material.