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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Radiation Processing of Formamide and Formamide:Water Ices on Silicate Grain Analogue
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Radiation Processing of Formamide and Formamide:Water Ices on Silicate Grain Analogue

机译：硅酸盐颗粒类似物对甲酰胺和甲酰胺的辐射处理：水冰

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Lyman-α (121.6 nm) photon and 1 keV electron-beam irradiation of pure HCONH_2 (FA) ice and H_2O:HCONH_2 ice mixtures on high-surface-area SiO_2 nanoparticles have been investigated with FT-IR spectroscopy and temperature programmed desorption (TPD). Lyman-α photolysis of pure amorphous FA ice grown at 70 K and crystalline FA ice produced by annealing to 165 K gives spectral signatures between 2120 and 2195 cm~(?1) that we assign primarily to OCN~? and CO. The OCN~? and CO yields are ～25% less abundant for crystalline FA ice. Photon and electron processing also produces H_2 that is released from the ice between ～90 and 140 K. A decrease in the H_2 TPD peak is seen for irradiated crystalline HCONH_2 ice. Lyman-α photolysis of H_2O:HCONH_2 mixed ices increases OCN~? and CO production, suggesting a catalytic role of H_2O. Also, for pure FA, 1 keV electron irradiation slightly increases the yield of OCN~?, while CO decarboxylation is selectively prevented. CO is also not produced in H_2O:HCONH_2 ices upon electron irradiation. Dissociative ionization, direct dissociative excitation, and dissociative electron attachment (DEA) channels are accessible in the Lyman-α (121.6 nm) photon and 1 keV electron-beam energy range. DEA energetically favors OCN~? and H~? formation, with the latter leading to H_2 formation. The FA fragment product identities, yields, and branching ratios are considerably different relative to the gas phase and depend upon the radiation type, ice structure, and the presence of SiO_2 nanoparticles. The latter may increase ion?electron recombination and radical recombination rates. The main products observed suggest very different condensed-phase dissociation channels from those reported for gas-phase dissociation. Formation of ions/products from FA is not negligible upon Lyman-α photolysis or electron irradiation, both of which could process ices in interstellar regions as well as in Titan's atmosphere.
机译：通过FT-IR光谱和程序升温脱附（TPD）研究了纯HCONH_2（FA）冰和H_2O：HCONH_2冰混合物在高表面积SiO_2纳米粒子上的Lyman-α（121.6 nm）光子和1 keV电子束辐照）。在70 K下生长的纯无定形FA冰和退火至165 K产生的结晶FA冰的Lyman-α光解作用产生2120和2195 cm〜（？1）之间的光谱特征，我们主要分配给OCN〜?。和CO。OCN〜？结晶FA冰的CO收率降低了约25％。光子和电子处理还会产生H_2，它会在约90至140 K之间从冰中释放出来。对于辐照的晶体HCONH_2冰，H_2 TPD峰会降低。 H_2O：HCONH_2混合冰的Lyman-α光解增加OCN〜？和CO的产生，表明H_2O具有催化作用。同样，对于纯FA，1 keV电子辐照会稍微增加OCN-α的收率，同时选择性地防止CO脱羧。在电子辐照下，H_2O：HCONH_2冰中也不会产生CO。在Lyman-α（121.6 nm）光子和1 keV电子束能量范围内，可使用离解电离，直接离解激发和离解电子附着（DEA）通道。 DEA大力支持OCN〜？和H〜？形成，后者导致H_2形成。 FA碎片产物的身份，收率和支化率相对于气相而言有很大不同，并且取决于辐射类型，冰结构和SiO_2纳米粒子的存在。后者可以提高离子-电子复合和自由基复合速率。观察到的主要产物表明冷凝相离解通道与气相分离所报告的通道截然不同。在莱曼-α光解或电子辐照下，由FA形成的离子/产物不可忽略，这两者都可以处理星际区域以及泰坦大气中的冰。

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