11:45 AM - 12:00 PM
[PPS07-10] UV irradiation experiments and mid-infrared imaging measurements of SO2 and C2H4 frost assuming the environments in the outer solar system
Keywords:Io, Mid-infrared, Laboratory experiment
Jupiter's moon Io is a volcanically active body, covered by a dilute sulfur oxide atmosphere (~10-3 Pa) dominated by SO2 (~90%) and SO2 frost. C2H4 has been observed by the Galileo and JUNO spacecraft to be present in the form of frost and atmospheric fog on exoplanetary bodies such as Titan and Pluto. C2H4 is known to exist in the form of frost and atmospheric fog on exoplanetary bodies such as Titan and Pluto. On the other hand, the chemical reactions and crystal growth processes of SO2/C2H4 in "solid" form on the surface of outer solar planets objects exposed to solar ultraviolet radiation have not been elucidated. This study aims to obtain mid-infrared spectra that can be compared with ground-based observations in the future by performing laboratory measurements that reproduce low-temperature atmosphere, surface frost, and UV irradiation.
In this study, we used an imaging Fourier transform mid-infrared spectrometer based on the associate common light path wavefront-division phase-shift interferometry (Qi et al., 2015) to measure the spatial two-dimensional transmission and absorption spectra of these molecules with wavelength resolution R=100, spatial resolution 12 μm and 3 mm diameter range. The experiment was performed in a liquid nitrogen dewar. The experiment was performed using a cryostat connected to a liquid nitrogen dewar with a small vacuum chamber inside, and the following procedure was used. (1) reduce the pressure in the chamber to ~10-3 Pa, (2) cool the temperature of the infrared transmission ZnSe sample stage to 90 K, (3) stop the pressure reduction and spray Ar-diluted SO2 or pure C2H4 gas onto the ZnSe, (4) leave the sample stage for 15 minutes after the gas is introduced and then reduce the pressure to (4) After the gas is introduced, the sample is left for 15 minutes and then depressurized, and the absorption spectrum of the deposited SO2 condensate is measured. The process in (4) is repeated. The results of annealing experiments and mid-infrared measurements of solid-state vibrational bands ( 7.4 μm, 8.7 μm) due to the SO2 reference vibration mode have been presented by Negishi et al. In addition to this experimental process, we will measure in-situ changes in the vibrational spectra appearing in the mid-infrared region while irradiating with UV light using a D2 lamp with a continuous spectrum up to 200-300 nm as a light source. By adjusting the duration of UV irradiation and the amount of frost deposition, we will clarify the relationship between the intensity and duration time of UV irradiation and the structural changes of SO2 and C2H4 frost.
In this study, we used an imaging Fourier transform mid-infrared spectrometer based on the associate common light path wavefront-division phase-shift interferometry (Qi et al., 2015) to measure the spatial two-dimensional transmission and absorption spectra of these molecules with wavelength resolution R=100, spatial resolution 12 μm and 3 mm diameter range. The experiment was performed in a liquid nitrogen dewar. The experiment was performed using a cryostat connected to a liquid nitrogen dewar with a small vacuum chamber inside, and the following procedure was used. (1) reduce the pressure in the chamber to ~10-3 Pa, (2) cool the temperature of the infrared transmission ZnSe sample stage to 90 K, (3) stop the pressure reduction and spray Ar-diluted SO2 or pure C2H4 gas onto the ZnSe, (4) leave the sample stage for 15 minutes after the gas is introduced and then reduce the pressure to (4) After the gas is introduced, the sample is left for 15 minutes and then depressurized, and the absorption spectrum of the deposited SO2 condensate is measured. The process in (4) is repeated. The results of annealing experiments and mid-infrared measurements of solid-state vibrational bands ( 7.4 μm, 8.7 μm) due to the SO2 reference vibration mode have been presented by Negishi et al. In addition to this experimental process, we will measure in-situ changes in the vibrational spectra appearing in the mid-infrared region while irradiating with UV light using a D2 lamp with a continuous spectrum up to 200-300 nm as a light source. By adjusting the duration of UV irradiation and the amount of frost deposition, we will clarify the relationship between the intensity and duration time of UV irradiation and the structural changes of SO2 and C2H4 frost.