Mid-infrared imaging spectroscopic measurements of C2H4 frost simulating the outer solar system environments

In the dense and cold atmosphere of Titan, the presence of C 2 H 4 haze has been confirmed by the observations of spacecraft. In the present study, original cryogenic experimental equipment was developed to simulate the low-temperature solid formation of C 2 H 4 in combination with in-situ infrared spectroscopic measurements. As a result, out-of-plane bending vibration ν 7 of solid-phase C 2 H 4 located at ~ 10.5 μm was successfully detected with high sensitivity, and two-dimensional spectrographs of C 2 H 4 at low temperatures were obtained. The obtained spectra of C 2 H 4 can be fitted to the double Lorentzian function with various heights, central wavelengths, and full widths at half the maximum (FWHM) of the two-component Lorentzian functions. They were classified into three types using the fitting parameters. However, their spectral shapes are different from the amorphous, metastable, and crystalline forms obtained by the previous laboratory experiment in terms of the distance of two peak wavelengths and FWHM. The results may link to understanding the spectral band properties of C 2 H 4 condensation in the haze component of Titan. Graphical Abstract