The principle objectives of my fellowship project are to measure and analyze the millimeter-wave rotational spectra of aminogen radicals CH2NH2 and CH3NH, which are potential reaction intermediates in the N chemistry in the interstellar medium leading to the synthesis of pre-biotic amino acids. Then the following experiment aim to investigate the reaction channels of these radicals with OH radical. To conduct these experiments, I need to develop an apparatus combining the chirped pulsed spectrometer, already developed in Lille before the start of the project, and the supersonic expansion technique coupled with direct current discharge. The expected results are the following: (a) spectral data, spectral model and line catalog of CH2NH2 and CH3NH; (b) understanding of reaction products between these radicals and the OH radical; (c) understanding of reaction channels between these radicals and the OH radical, i.e. the yield of each kind of reaction product, if the reaction leads to multiple different products.
The Covid-19 pandemic and then the subsequent ending of the transition period of Brexit in the winter of 2020 have posed significant influence on the project progress, delaying the main research task by 1 year. The delay made me unable to complete the planned research tasks and I had to seek deviation of the plan. For the planned research, I have accomplished to ~40% of the plan, which is at the stage before D1.3 in WP1. For the deviations, I chose to develop a general spectral treatment function that can help improving the signal to noise ratio of the chirped pulse data, and to study the spectra of formaldoxime (CH2NOH), nitrosomethane (CH3NO), and the 3-carbon imine 2-propanimine ((CH3)2CNH), which might be reaction products of the aminogen radical with OH, and which did not have precise millimeter-wave spectra available. These molecules themselves are also of astrochemistry interest and can be searched in the interstellar medium. By doing so, I have expanded the known molecular line catalogs, which will be beneficial for the identification of reaction products when this stage of experiment will finally be conducted in the future.
The main scientific achievements of this project so far are the following: (1) the development of a general spectral treatment function that improves signal to noise ratio of chirped pulse spectra; (2) the first laboratory measurement and analysis of 3 important isomers of N-bearing astrophysical molecules, CH2NOH, CH3NO, and (CH3)2CNH (Figures 1 and 2), in the millimeter-wave range; (3) the implementation of the instrument and software and reproduction of radical species CH2CN (Figure 3) and CH3CO.
The results of the project, mainly from the deviations I chose to compensate the extreme delay posed on the project, will be used by the astronomical and spectroscopic community as line catalogs, a line by line spectral database, for the identification of the studied molecules in the interstellar medium and in gas-phase chemical reaction systems. The spectral treatment function may be used by a broader community as a way to improve the quality of experimental data, if the experiment applies physics principle similar to the chirped pulse technique.
