IBER 2023

Simulating interstellar temperatures in the laboratory to study the gas-phase OH+NH2CHO reaction

6 Sept 2023, 18:35

1h

Department of Physics, University of Coimbra

Poster Communication Poster Session

Speaker

Sara Espinosa Gómez (UNIVERSIDAD DE CASTILLA-LA MANCHA)

Description

The kinetic study of neutral-neutral reactions in the gas phase at ultralow temperatures is undergoing a huge advancement over the last decades [1]. Such studies have exponentially increased due to the increasing number of new molecules detected in the interstellar medium (ISM), specially in the coldest regions (10-100 K). To model the chemistry occurring in these extreme environments, the formation and destruction routes for IS molecules have to be characterized by means of the rate coefficient, k(T), a crucial parameter to be included in astrochemical networks. For most neutral-neutral reactions, k(T) is usually extrapolated down to 10 K from kinetic data reported at high temperatures (>200-300 K). However, this procedure usually fails and k(10 K) is underestimated by several orders of magnitude, which obviously comes up with dramatic consequences in IS chemical modelling. For that reason, mimicking interstellar conditions in the laboratory and measuring accurate k(T) are essential. First, a suitable technique, such as the so-called CRESU (French acronym for Reaction Kinetics in a Uniform Supersonic Flow) is used to achieve the very low temperatures of the ISM to determine k(T) as a function of T [2]. In this work, a pulsed CRESU system has been employed to study the temperature dependence of k(T) between 11.7 and 177.5 K for the reaction of formamide (NH${}_2$CHO) with hydroxyl (OH) radicals, key intermediates in IS chemical processes. It is thought that NH${}_2$CHO, which was first detected towards Sagittarius B molecular cloud [3], can play a crucial role in the formation of prebiotic molecules in space. The available experimental k(T) for the titled reaction is scarce and only reported around 300 K [4,5]. However, theorical calculations predict an increase of k(T) when temperature decreases in the 200-350 K range [5]. Our kinetic study in the low-temperature range confirms that below 200 K, k(T) increases when temperature is lower, with an increase of k(T) in the whole temperature range with respect to k(300 K). The observed T-dependence of k(T) will be discussed and an expression for its use in pure- and gas-grain astrochemical models will be provided.

References
[1] B. R. Rowe, A. Canosa, D. E. Heard, Uniform Supersonic Flows in Chemical Physics, World Scientific, Europe, 2022.
[2] E. Jiménez, B. Ballesteros, A. Canosa, T. M. Townsend, F. J. Maigler, V. Napal, B. R. Rowe, J. Albaladejo, Rev. Sci. Instrum. 86 (2015) 045108 1-10.
[3] R. H. Rubin, G. W. Swenson, Jr, R. C. Solomon, H. L. Flygare. Astrophys. J. 169 (1971) L39-L44.
[4] N. Borduas, G. Da Silva, J. G. Murphy, J. P. D. Abbatt, J. Phys. Chem. A 119 (2015) 4298-4308.
[5] A. J. C. Bunkan, T. Mikoviny, C. J. Nielsen, A. Wisthaler, L. Zhu, J. Phys. Chem. A 120 (2016) 1222-1230.