An Expanded Gas-grain Model for Interstellar Glycine

Abstract

The study of the chemical evolution of glycine in the interstellar medium is one of challenging topics in astrochemistry. Here, we present the chemical modeling of glycine in hot cores using the state-of-the-art three-phase chemical model NAUTILUS, which is focused on the latest glycine chemistry. For the formation process of glycine on the grain surface, we obtained consistent results with previous studies that glycine would be formed via the reactions of COOH with CH 2 NH 2 . However, we will report three important findings regarding the chemical evolution and the detectability of interstellar glycine. First, with the experimentally obtained binding energy from the temperature programmed thermal desorption (TPD) experiment, a large proportion of glycine was destroyed through the grain surface reactions with NH or CH 3 O radicals before it fully evaporates. As a result, the formation process in the gas phase is more important than thermal evaporation from grains. If this is the case, NH 2 OH and CH 3 COOH rather than CH 3 NH 2 and CH 2 NH would be the essential precursors to the gas phase glycine. Secondly, since the gas phase glycine will be quickly destroyed by positive ions or radicals, early evolutionary phase of the hot cores would be the preferable target for the future glycine surveys. Thirdly, we suggest the possibility that the suprathermal hydrogen atoms can strongly accelerate the formation of COOH radicals from CO 2 , resulting in the dramatic increase of formation rate of glycine on grains. The efficiency of this process should be investigated in detail by theoretical and experimental studies in the future.

Control of Chemical Forms of Tritium in FLiNaK under Low Flux Neutron Irradiation

“…H 2 % which was obtained for solid FLiBe at 573 K [8]. The ratio of HT to soluble tritium obtained in this study is more than 3 times larger than the result for FLiBe at 873 K using a He+H 2 (0.1%) gas [2]. The difference in the rate coefficient and the ratio of HT to soluble tritium may be because of the difference in temperature of the salts or chemical structure in the salts (e.g., the presence of polyatomic ions in FLiBe).…”

“…YAYOI of the University of Tokyo [1][2][3]. The previous research has shown the change in chemical forms of tritium released from FLiBe under various H 2 concentrations in sweep gases.…”

Discovery in space of ethanolamine, the simplest phospholipid head group

“…The gray shaded area corresponds to a hydrogenation chain. The chemical reactions indicated with colored arrows have been proposed in previous work: magenta ( 36 ), blue ( 38 ), orange ( 41 ), cyan ( 39 ), and green ( 41 , 47 ). In black, we show the formation routes proposed in this work.…”

“…We note that the barrierless CH + CO reaction proposed by ref. 41 might also contribute to the formation of CHCO ( Fig. 5 ).…”

Toward the RNA-World in the Interstellar Medium—Detection of Urea and Search of 2-Amino-oxazole and Simple Sugars

“…Since both UV and cosmic ray irradiations yield a similar chemistry and COM composition in interstellar ices (Muñoz Caro et al, 2014), our measured upper limit to the abundance of NH 2 CH 2 COOH suggests that ice irradiation may not produce NH 2 CH 2 COOH efficiently in the ISM. Alternatively, this molecule could form on irradiated interstellar ices but, once injected into the gas phase by protostellar feedback, NH 2 CH 2 COOH could be destroyed quickly by ions and radicals (Garrod, 2013;Suzuki et al, 2018). In contrast to NH 2 CH 2 COOH, DHA and CHOCHOH-CH 2 OH have only been searched for toward the SgrB2 N-LMH massive hot core (Hollis et al, 2004;Widicus Weaver and Blake, 2005;Apponi et al, 2006).…”