Vishwakarma Gaurav, Malla Bijesh K, Kumar Rajnish, Pradeep Thalappil
DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE), Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India.
Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036, India.
Phys Chem Chem Phys. 2024 Jun 6;26(22):16008-16016. doi: 10.1039/d4cp01414f.
Clathrate hydrates (CHs), host-guest compounds of water forming hydrogen-bonded cages around guest molecules, are now known to exist under interstellar conditions. Experimental evidence demonstrated that prolonged thermal treatment of a solid mixture of water and CO/CH produces CHs at 10-30 K under simulated interstellar conditions. However, in the current study, we show that CO produced photochemically by vacuum ultraviolet irradiation of HO-CO mixtures at 10 K and ∼10 mbar, gets partitioned into its CH phase and a matrix phase embedded in amorphous ice. The process occurring under simulated interstellar conditions was studied at different temperatures and HO-CO compositions. The formation of CO CH and other photoproducts was confirmed using reflection absorption infrared spectroscopy. The UV-induced photodesorption event of CO may provide the mobility required for the formation of CHs, while photoproducts like methanol can stabilize such CH structures. Our study suggests that new species originating during such energetic processing in ice matrices may form CH, potentially altering the chemical composition of astrophysical environments.
笼形水合物（CHs）是水的主客体化合物，在客体分子周围形成氢键笼，现在已知其存在于星际条件下。实验证据表明，在模拟星际条件下，对水与CO/CH的固体混合物进行长时间热处理，会在10 - 30K产生笼形水合物。然而，在当前研究中，我们表明，在10K和约10毫巴的条件下，通过对HO-CO混合物进行真空紫外辐照光化学产生的CO，会被分配到其笼形水合物相和嵌入无定形冰中的基质相中。在不同温度和HO-CO组成条件下研究了模拟星际条件下发生的过程。使用反射吸收红外光谱法确认了CO笼形水合物和其他光产物的形成。CO的紫外诱导光解吸事件可能为笼形水合物的形成提供所需的迁移率，而甲醇等光产物可以稳定这种笼形水合物结构。我们的研究表明，在冰基质中这种高能处理过程中产生的新物种可能形成笼形水合物，从而可能改变天体物理环境的化学成分。
