LOW TEMPERATURE REACTION KINETICS OF CN(v=1) WITH BUTADIENE ISOMERS.

Thawoos, Shameemah

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Title

LOW TEMPERATURE REACTION KINETICS OF CN(v=1) WITH BUTADIENE ISOMERS.

Author(s)

Thawoos, Shameemah

Contributor(s)

• Suits, Arthur
• Cavallotti, Carlo
• Hall, Gregory

Issue Date

2023-06-21

Keyword(s)

Dynamics and kinetics

Abstract

Formation pathways and mechanisms of unsaturated nitrogen-containing compounds at very low temperatures are of great interest in the field of astrochemistry. The reaction of butadiene isomers with CN is one such reaction class that can be a key elementary step in the formation of large nitrogen rich molecules of potential biological importance in astrochemical environments. We present a joint experimental and theoretical investigation of reaction kinetics of vibrationally excited CN with 1,3 and 1,2-butadiene isomers at 70 K. The experimental method involves a newly built apparatus that couples a pulsed uniform supersonic flow with a continuous wave cavity ringdown spectrometer (UF-CRDS). The well-matched hydrodynamic time of the uniform flow with the long ringdown time decay allows the measurement of the complete kinetics over observation times up to 200 µs on each ringdown decay, an approach termed SKaR (Simultaneous kinetics and ringdown). The vibrationally excited CN is produced by photolyzing BrCN with a 248 nm excimer laser. The adjustable butadiene density greatly exceeds that of the photolytic CN radicals, ensuring pseudo first order conditions for the loss of CN. The time-dependent density of CN(v=1, j=5.5) is probed by tuning the DFB diode laser at 7070.24 cm−¹, the R₁(5.5), line of the (0-1) band of A²Π–X²Σ⁺ electronic transition. The measured bimolecular rates are (3.96 ± 0.28) x 10−¹⁰ and (3.06 ± 0.35) x 10−¹⁰ cm³ molecule−¹ s−¹ for 1,3 and 1,2-butadiene, respectively. The experimental rates were modeled by VRC-TST (Variable Reaction Coordinate Transition State Theory) calculations on a high-level multireference potential energy surface. For the 1,2-butadiene case the entrance channel branching was combined with earlier predictions of branching following the decays of the initial adducts to predict the overall branching.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

eng

Handle URL

https://hdl.handle.net/2142/122406

DOI

https://doi.org/10.15278/isms.2023.6966

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