Erukala Swetha, Feinberg Alexandra J, Moon Cheol Joo, Choi Myong Yong, Vilesov Andrey F
Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
Core-Facility Center for Photochemistry and Nanomaterials, Department of Chemistry (BK21 FOUR), Research Institute of Natural Sciences, Gyeongsang National University, Jinju, Republic of Korea.
J Chem Phys. 2022 May 28;156(20):204306. doi: 10.1063/5.0091819.
Helium droplets are unique hosts for isolating diverse molecular ions for infrared spectroscopic experiments. Recently, it was found that electron impact ionization of ethylene clusters embedded in helium droplets produces diverse carbocations containing three and four carbon atoms, indicating effective ion-molecule reactions. In this work, similar experiments are reported but with the saturated hydrocarbon precursor of ethane. In distinction to ethylene, no characteristic bands of larger covalently bound carbocations were found, indicating inefficient ion-molecule reactions. Instead, the ionization in helium droplets leads to formation of weaker bound dimers, such as (CH)(CH), (CH)(CH), and (CH)(CH), as well as larger clusters containing several ethane molecules attached to CH , CH , and CH ionic cores. The spectra of larger clusters resemble those for neutral, neat ethane clusters. This work shows the utility of the helium droplets to study small ionic clusters at ultra-low temperatures.
氦滴是用于红外光谱实验中分离各种分子离子的独特宿主。最近发现，嵌入氦滴中的乙烯团簇经电子碰撞电离会产生含有三个和四个碳原子的各种碳正离子，这表明发生了有效的离子 - 分子反应。在这项工作中，报告了类似的实验，但使用乙烷作为饱和烃前体。与乙烯不同，未发现较大共价键合碳正离子的特征谱带，这表明离子 - 分子反应效率低下。相反，氦滴中的电离导致形成较弱键合的二聚体，如(CH)(CH)、(CH)(CH)和(CH)(CH)，以及包含几个乙烷分子连接到CH、CH和CH离子核的更大团簇。更大团簇的光谱类似于中性纯乙烷团簇的光谱。这项工作展示了氦滴在超低温下研究小离子团簇的实用性。
