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

Abstract

Abstract In the dense and cold atmosphere of Titan, the presence of C2H4 haze has been confirmed by the observations of satellite explorers. In the present study, an original cryogenic experimental equipment was developed to simulate the low-temperature solid formation of C2H4 in combination with in-situ infrared spectroscopic measurements to understand the spectral band properties of C2H4 condensation in the haze component of Titan. As a result, out-of-plane bending vibration ν7 of solid-phase C2H4 located at λ ~ 10.5 µm was successfully detected with high sensitivity, and two-dimensional spectrographs of C2H4 at low temperatures were obtained. The obtained spectra of C2H4 can be fitted to the double Lorentzian function with various heights, central wavelengths, and full widths at half maximum of the two-component Lorentzian functions. They were classified into three types whose spectral shapes are similar to the amorphous, metastable crystal, and crystalline forms obtained by the previous laboratory experiment.