A Complete Quantification of Photon-induced Desorption Processes of CO2 Ice

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/77121

Title:	A Complete Quantification of Photon-induced Desorption Processes of CO2 Ice
Authors:	謝妮恩;Sie, Ni-En
Contributors:	物理學系
Keywords:	二氧化碳;星際物質;光脫附;真空紫外光照射;紅外光譜儀;四極質譜儀;Carbon dioxide;interstellar medium;photodesorption;VUV irradiation;FTIR;QMS
Date:	2018-08-20
Issue Date:	2018-08-31 13:57:53 (UTC+8)
Publisher:	國立中央大學
Abstract:	在冷星雲及星際物質之間，大量的二氧化碳被觀測到以氣態的形式出現，原因來自於宇宙射線和真空紫外光的照射，而二氧化碳的光脫附包含了化學反應的資訊，在恆星與星際冰晶形成的區域擔任重要的角色。根據文獻，不同溫度下形成的二氧化碳冰晶將導致結構不同，在35 K以下的結構是無序的，而在35 K之上形成的二氧化碳冰晶是有序的晶格排列。以往文獻指出，二氧化碳的光脫附產量與結構有關，為了深入探討二氧化碳結構與光脫附的關係，將二氧化碳分別在16、30、40、50和 60 K的溫度下生長，接著降回16 K照射真空紫外光，搭配紅外光譜儀和質譜儀量測不同結構下二氧化碳冰晶的光脫附產量。由於以往質譜儀的脫附值僅代表相對的值，本篇論文中提出了一個新穎的方式校正質譜儀，能夠將量測到的電流訊號轉換成多少分子脫附出來。實驗結果說明最主要的光脫附產物為一氧化碳、氧氣及二氧化碳，在不同溫度生長的二氧化碳冰晶中，這三種分子的光脫附產量幾乎相同，這也代表著二氧化碳結構對於光脫附產量是沒有影響的，而此結果和以往的文獻是相反的。 ;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.
Appears in Collections:	[Graduate Institute of Physics] Electronic Thesis & Dissertation

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