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Direct Measurements of Activation Energies for Surface Diffusion of CO and CO2 on Amorphous Solid Water Using In Situ Transmission Electron Microscopy
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| Title: | Direct Measurements of Activation Energies for Surface Diffusion of CO and CO2 on Amorphous Solid Water Using In Situ Transmission Electron Microscopy |
| Authors: | Kouchi, Akira Browse this author →KAKEN DB | | Furuya, Kenji Browse this author | | Hama, Tetsuya Browse this author | | Chigai, Takeshi Browse this author →KAKEN DB | | Kozasa, Takashi Browse this author | | Watanabe, Naoki Browse this author →KAKEN DB |
| Keywords: | Astrochemistry | | Reaction rates | | Experimental techniques | | Ice formation | | Theoretical models | | Laboratory astrophysics | | Interdisciplinary astronomy | | Interstellar molecules | | Dense interstellar clouds |
| Issue Date: | 1-Mar-2020 |
| Publisher: | IOP Publishing |
| Journal Title: | Astrophysical journal letters |
| Volume: | 891 |
| Issue: | 1 |
| Start Page: | L22 |
| Publisher DOI: | 10.3847/2041-8213/ab78a2 |
| Abstract: | The importance of the activation energy of surface diffusion (E-sd) of adsorbed molecules on amorphous solid water (ASW) has been widely discussed in terms of chemical reactions on ASW at low temperatures. However, in previous work, E-sd has not been measured directly but estimated from indirect experiments. It has been assumed in chemical network calculations that E-sd is between 0.3 and 0.8 of the desorption energies of a molecule. It remains important to obtain direct measurements of E-sd. We performed in situ observations of the deposition process of CO and CO2 on ASW using transmission electron microscopy (TEM) and deduced the E-sd of CO and CO2 on ASW to be 350 50 and 1500 100 K, respectively. The value of E-sd of CO is approximately 0.3 of the total adsorption energy of CO on ASW, i.e., much smaller than assumed in chemical network calculations, where the corresponding figure is 575 K, assuming approximately 0.5 of the desorption energy. We demonstrated that TEM is very useful not only for the observation of ices but also for the measurement of some physical properties that are relevant in astrochemistry and astrophysics. Using the E-sd of CO measured in the present study (350 K), we have updated the chemical network model of Furuya et al., confirming that CO2 could be efficiently formed by the reaction CO + OH -> CO2 + H in the initial stages of the evolution of molecular clouds. |
| Type: | article |
| URI: | http://hdl.handle.net/2115/80512 |
| Appears in Collections: | 低温科学研究所 (Institute of Low Temperature Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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Submitter: 香内 晃
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