Rotational spectral studies of O(1D) insertion reactions with methane and ethylene: Methanol and vinyl alcohol in a supersonic expansion

Abstract

a b s t r a c tWe report a new apparatus for millimeter/submillimeter spectroscopic studies of O( 1 D) insertion reactions to produce molecules of astrophysical interest. This study focuses on the insertion of O( 1 D) into methane to form methanol, and the insertion of O( 1 D) into ethylene to form vinyl alcohol (CH 2 CHOH). The O( 1 D) was produced via laser photodissociation of O 3 in a fused silica tube and mixed with a hydrocarbon before a supersonic expansion. Direct absorption millimeter/submillimeter spectroscopy was used to monitor the products. The methanol study was used as an experimental benchmark, while the vinyl alcohol study extended rotational spectroscopic measurements to higher frequencies. Observed products from both insertion reactions included, but were not limited to, H 2 CO, HO 2 , and CH 3 O. Methanol and vinyl alcohol were only produced in detectable quantities when the fused silica tube was included, indicating that collisions before the expansion are required for production and stabilization of the O( 1 D) insertion products.

Methanol Formation via Oxygen Insertion Chemistry in Ices

“…CH 3 OH formation: In the gas phase the insertion of O( 1 D) into CH 4 results in an excited CH 3 OH product, which undergoes unimolecular dissociation to form mainly OH + CH 3 unless it is stabilized by e.g. collision (DeMore & Raper 1967;Parnis et al 1993) or supersonic expansion (Hays et al 2015). As our experiments involve condensed ices, it is fully consistent that the intact CH 3 OH molecule is observed due to energy dissipation into the solid.…”

“…collision (DeMore & Raper 1967;Parnis et al 1993) or supersonic expansion (Hays et al 2015). As our experiments involve condensed ices, it is fully consistent that the intact CH 3 OH molecule is observed due to energy dissipation into the solid.…”

“…Indeed, following CH 3 OH, H 2 CO is the next most stable possible product of O( 1 D) insertion into CH 4 (Chang & Lin 2002;Yu & Muckerman 2004), and gas-phase and matrix studies typically show H 2 CO as the second-most common insertion product (e.g. DeMore & Raper 1967;Appelman et al 1989;Hays et al 2015). Moreover, from Figure 6 the shape of the H 2 CO growth curve is different from the second-generation product CO 2 , but quite similar to that of the primary insertion product CH 3 OH.…”

Astronomical Search of Vinyl Alcohol Assisted by Submillimeter Spectroscopy

“…Line catalogs based on these works are present in the Cologne Database for Molecular Spectroscopy (CDMS) . In addition, a set of refined spectroscopic constants is available from Hays et al for syn -VA. Using the available parameters and dipole moment components from Saito, the spectra of syn - and anti -VA were predicted at millimeter and submillimeter frequencies using the SPFIT/SPCAT suite of programs …”

“…Ground-state rotational transitions of both conformers were recorded in the frequency region of 245–310 GHz and involve energy levels with J values spanning from 2 to 38 and K a values from 0 to 13. For each conformer, the newly observed transition frequencies, along with data previously reported, ,− , have been analyzed using a standard semi-rigid Watson S -reduced Hamiltonian, suitable for a nearly prolate asymmetric rotor, such as VA. For the purpose of this work, centrifugal distortion terms up to the sextic power of the rotational angular momentum were used.…”