| Summary: | 碩士 === 國立中央大學 === 物理學系 === 106 === In cold dense cloud and interstellar medium (ISM), CO2 is observed to be one of the most abundant gas molecule due to irradiation of cosmic ray or ultraviolet (UV) photons, and the photodesorption of CO2 ice contains the information of chemical reactions in the star and interstellar forming regions. According to literatures, different deposition temperatures of CO2 ice lead to distinct structures of CO2, which possesses an amorphous structure below 35 K and a crystalline structure at temperatures higher than 35 K, and the photodesorption yield of CO2 ice depends on its morphology. For the purpose of investigating the relationship between the photodesorption yield of CO2 ice and its morphology, CO2 ice is deposited at 16, 30, 40, 50, and 60 K respectively, irradiated by vacuum ultraviolet (VUV) photons at 16 K, with detection systems of a Fourier transform infrared spectroscopy (FTIR) and a quadrupole mass spectrometry (QMS).
In this work, we introduce a novel method to transfer the relative value into authentic photodesorption yield by quantitative calibration of QMS. The experimental results show that the dominant photodesorbed species is CO molecules, along with CO2 and O2, and the photodesorption yields of CO2 ices deposited at different temperature configurations are almost the same, meaning that the morphology effect has nothing to do on photodesorption yield of CO2 ice, which is inconsistent with previous works.
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