High-resolution infrared spectroscopy of jet cooled trans-deuteroxycarbonyl (trans-DOCO) radical

Author
Abstract
The rovibrational spectrum of jet cooled<em>trans</em>-deuteroxycarbonyl (<em>trans</em>-DOCO) radical has been explored at suppressed-Doppler resolution via direct infrared absorption spectroscopy. The <em>trans</em>-DOCO is produced in a supersonic slit discharge of rare-gas/CO mixture doped with D<sub>2</sub>O, whereby the OD forms an energized adduct with CO, cooling in the supersonic expansion and stabilizing DOCO in the <em>trans</em> well. Active laser-frequency stabilization and collisional quenching of Doppler broadening along the slit axis yield \&lt;10 MHz frequency precision, with the absorbance noise approaching the quantum shot-noise limit. The current high-resolution spectral results are in excellent agreement with recent studies of the <em>trans</em>-DOCO radical by infrared frequency comb spectroscopy under room temperature conditions [Bui <em>et al.</em>, Mol. Phys. 116, 3710 (2018)]. Combined with previous microwave/millimeter wave rotational studies, the suppressed-Doppler infrared data permit characterization of the vibrational ground state, improved structural parameters for the OD stretch vibrational level, and<em>trans</em>-DOCO spin-rotation information in both ground and excited vibrational states. Additionally, the infrared data reveal a-type and much weaker b-type contributions to the spectrum, analysis of which yields orientation of the OD stretch transition dipole moment in the body fixed frame. Of dynamical interest is whether the nascent\&nbsp;<em>trans</em>-DOCO complex formed in the entrance channel has sufficient time to convert into the\&nbsp;<em>cis</em>-DOCO isomer, or whether this is quenched by rapid stabilization into the<em>trans</em>-DOCO well. <em>Ab initio</em> and Rice-Ramsperger-Kassel-Marcus analysis of the intrinsic reaction coordinate for<em>trans</em>-DOCO to <em>cis</em>-DOCO interconversion rates supports the latter scenario, which helps explain the failure of previous high resolution infrared efforts to detect <em>cis</em>-hydroxycarbonyl.</p>
Year of Publication
2019
Journal
The Journal of Chemical Physics
Volume
150
Number of Pages
194304
Date Published
2019-05
ISSN Number
0021-9606
URL
https://aip.scitation.org/doi/10.1063/1.5092599
DOI
10.1063/1.5092599
JILA PI
Associated Institutes
Journal Article