紫外辐射甲烷（CH4）冰中较大物种的光子诱导解吸
Photon-induced desorption of larger species in UV-irradiated methane (CH4) ice
摘要：
在致密云内部和星周区域的低温下，除了H $_2$ O和少量的CO、CO $_2$或CH $_3$ OH等物质外，还在冰质尘埃颗粒上观测到CH $_4$的红外特征。紫外光子在冰幔中引起不同的过程，影响在气相中检测到的分子丰度。这项工作的目的是了解发生在一个纯CH $_4$冰地幔提交紫外线照射的过程。我们研究了紫外光照射下冰中产生的不同光致产物的光子诱导过程。实验是在ISAC中进行的，ISAC是一个超高真空室，配备有低温恒温器和F型紫外灯，再现了宇宙射线在稠密云中引起的次级紫外场。红外光谱和四极质谱分别用于监测冰的形成、辐照和升温过程中的固相和气相。未观察到纯CH $_4$的直接光解吸。UV光子形成CH $_x\cdot$和H $\cdot$自由基，产生光产物如H $_2$、C $_2$ H $_2$、C $_2$ H $_6$和C $_3$ H $_8$。发现了C $_2$ H $_2$的光脱附和C $_2$ H $_6$和C $_3$ H $_8$的光化学吸附的证据，后者是迄今为止发现的最大的光化学吸附分子。还进行了$^{13}$ CH $_4$实验以确认这些结果的可靠性。
英文摘要：
At the low temperatures found in the interior of dense clouds and circumstellar regions, along with H$_2$O and smaller amounts of species such as CO, CO$_2$, or CH$_3$OH, the infrared features of CH$_4$ have been observed on icy dust grains. Ultraviolet (UV) photons induce different processes in ice mantles, affecting the molecular abundances detected in the gas-phase. This work aims to understand the processes that occur in a pure CH$_4$ ice mantle submitted to UV irradiation. We studied photon-induced processes for the different photoproducts arising in the ice upon UV irradiation. Experiments were carried out in ISAC, an ultra-high vacuum chamber equipped with a cryostat and an F-type UV-lamp reproducing the secondary UV-field induced by cosmic rays in dense clouds. Infrared spectroscopy and quadrupole mass spectrometry were used to monitor the solid and gas-phase, respectively, during the formation, irradiation, and warm-up of the ice. Direct photodesorption of pure CH$_4$ was not observed. UV photons form CH$_x\cdot$ and H$\cdot$ radicals, leading to photoproducts such as H$_2$, C$_2$H$_2$, C$_2$H$_6$, and C$_3$H$_8$. Evidence for the photodesorption of C$_2$H$_2$ and photochemidesorption of C$_2$H$_6$ and C$_3$H$_8$ was found, the latter species is so far the largest molecule found to photochemidesorb. $^{13}$CH$_4$ experiments were also carried out to confirm the reliability of these results.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
