Dataset Information

Experimental and Theoretical Investigation of the Reaction of NH₂ with NO at Very Low Temperatures.

ABSTRACT: The first experimental study of the low-temperature kinetics of the gas-phase reaction between NH₂ and NO has been performed. A pulsed laser photolysis-laser-induced fluorescence technique was used to create and monitor the temporal decay of NH₂ in the presence of NO. Measurements were carried out over the temperature range of 24-106 K, with the low temperatures achieved using a pulsed Laval nozzle expansion. The negative temperature dependence of the reaction rate coefficient observed at higher temperatures in the literature continues at these lower temperatures, with the rate coefficient reaching 3.5 × 10^-10 cm³ molecule^-1 s^-1 at T = 26 K. Ab initio calculations of the potential energy surface were combined with rate theory calculations using the MESMER software package in order to calculate and predict rate coefficients and branching ratios over a wide range of temperatures, which are largely consistent with experimentally determined literature values. These theoretical calculations indicate that at the low temperatures investigated for this reaction, only one product channel producing N₂ + H₂O is important. The rate coefficients determined in this study were used in a gas-phase astrochemical model. Models were run over a range of physical conditions appropriate for cold to warm molecular clouds (10 to 30 K; 10⁴ to 10⁶ cm^-3), resulting in only minor changes (<1%) to the abundances of NH₂ and NO at steady state. Hence, despite the observed increase in the rate at low temperatures, this mechanism is not a dominant loss mechanism for either NH₂ or NO under dark cloud conditions.

SUBMITTER: Douglas KM

PROVIDER: S-EPMC10476206 | biostudies-literature | 2023 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Experimental and Theoretical Investigation of the Reaction of NH2 with NO at Very Low Temperatures.

Douglas Kevin M KM Lucas Daniel D Walsh Catherine C Blitz Mark A MA Heard Dwayne E DE

The journal of physical chemistry. A 20230817 34

The first experimental study of the low-temperature kinetics of the gas-phase reaction between NH2 and NO has been performed. A pulsed laser photolysis-laser-induced fluorescence technique was used to create and monitor the temporal decay of NH2 in the presence of NO. Measurements were carried out over the temperature range of 24-106 K, with the low temperatures achieved using a pulsed Laval nozzle expansion. The negative temperature dependence of the reaction rate coeffici ...[more]

PMID: 37589656

Similar Datasets

Project description:Rate coefficients for the reaction of C2H with CH2O were measured for the first time over the temperature range of 37-603 K, with the C2H radicals produced by pulsed laser photolysis and detected by CH radical chemiluminescence following their reaction with O2. The low temperature measurements (≤93 K) relevant to the interstellar medium were made within a Laval nozzle gas expansion, while higher temperature measurements (≥308 K) were made within a temperature controlled reaction cell. The rate coefficients display a negative temperature dependence below 300 K, reaching (1.3 ± 0.2) × 10-10 cm3 molecule-1 s-1 at 37 K, while only a slight positive temperature dependence is observed at higher temperatures above 300 K. Ab initio calculations of the potential energy surface (PES) were combined with rate theory calculations using the MESMER master-equation program in order to predict rate coefficients and branching ratios. The three lowest energy entrance channels on the PES all proceed via the initial formation of a weakly bound prereaction complex, bound by ∼5 kJ mol-1, followed by either a submerged barrier on the route to the H-abstraction products (C2H2 + CHO), or emerged barriers on the routes to the C- or O-addition species. MESMER calculations indicated that over the temperature range investigated (10-600 K) the two addition channels were uncompetitive, accounting for less 0.3% of the total product yield even at 600 K. The PES containing only the H-abstraction product channel was fit to the experimentally determined rate coefficients, with only a minor adjustment to the height of the submerged barrier (from -2.6 to -5.9 kJ mol-1) required. Using this new submerged barrier height, and including the subsequent dissociation of the CHO product into CO + H in the PES, rate coefficients and branching ratios were calculated over a wide range of temperatures and pressures and these used to recommend best-fit modified Arrhenius expressions for use in astrochemical modeling. Inclusion of the new rate coefficients and branching ratios in a UMIST chemical model of an outflow from an asymptotic giant branch (AGB) star yielded no significant changes in the abundances of the reactants or the products of the reaction, however, removal of the C-addition channel currently in the UMIST Rate22 database did result in a significant reduction in the abundance of propynal (HCCCHO).

Dataset Information

Experimental and Theoretical Investigation of the Reaction of NH₂ with NO at Very Low Temperatures.

Publications

Experimental and Theoretical Investigation of the Reaction of NH<sub>2</sub> with NO at Very Low Temperatures.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets