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Gas-Phase Reactivity of OH Radicals With Ammonia (NH3) and Methylamine (CH3NH2) at Around 22 K
Interstellar molecules containing N atoms, such as ammonia (NH 3 ) and methylamine (CH 3 NH 2 ), could be potential precursors of amino acids like the simplest one, glycine (NH 2 CH 2 COOH). The gas-phase reactivity of these N-bearing species with OH radicals, ubiquitous in the interstellar medium,...
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| Published in: | Frontiers in astronomy and space sciences 2022-01, Vol.8 |
|---|---|
| Main Authors: | , , , , |
| Format: | Article |
| Language: | English |
| Subjects: | |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | Interstellar molecules containing N atoms, such as ammonia (NH
3
) and methylamine (CH
3
NH
2
), could be potential precursors of amino acids like the simplest one, glycine (NH
2
CH
2
COOH). The gas-phase reactivity of these N-bearing species with OH radicals, ubiquitous in the interstellar medium, is not known at temperatures of cold dark molecular clouds. In this work, we present the first kinetic study of these OH-reactions at around 22 K and different gas densities [(3.4–16.7) × 10
16
cm
−3
] in helium. The obtained rate coefficients, with ± 2σ uncertainties, can be included in pure gas-phase or gas-grain astrochemical models to interpret the observed abundances of NH
3
and CH
3
NH
2
. We observed an increase of
k
1
and
k
2
with respect to those previously measured by others at the lowest temperatures for which rate coefficients are presently available: 230 and 299 K, respectively. This increase is about 380 times for NH
3
and 20 times for CH
3
NH
2
. Although the OH + NH
3
reaction is included in astrochemical kinetic databases, the recommended temperature dependence for
k
1
is based on kinetic studies at temperatures above 200 K. However, the OH + CH
3
NH
2
reaction is not included in astrochemical networks. The observed increase in
k
1
at ca. 22 K does not significantly change the abundance of NH
3
in a typical cold dark interstellar cloud. However, the inclusion of
k
2
at ca. 22 K, not considered in astrochemical networks, indicates that the contribution of this destruction route for CH
3
NH
2
is not negligible, accounting for 1/3 of the assumed main depletion route (reaction with HCO
+
) in this IS environment.
k
1
(
OH+N
H
3
)
=
(
2.7
±
0.1
)
×
10
−
11
c
m
3
s
-1
k
2
(
OH+C
H
3
N
H
2
)
=
(
3.9
±
0.1
)
×
10
−
10
c
m
3
s
-1 |
|---|---|
| ISSN: | 2296-987X 2296-987X |
| DOI: | 10.3389/fspas.2021.802297 |