Low-energy inelastic collisions of OH radicals with He atoms and D$_2$ molecules

TL;DR

This study experimentally measures the rotational inelastic scattering of OH radicals with He and D2 at low energies, validating quantum calculations for the OH-He system and providing detailed state-to-state cross sections.

Contribution

It provides precise experimental data on inelastic scattering cross sections for OH with He and D2, confirming theoretical calculations for the OH-He interaction.

Findings

Validated quantum calculations for OH-He inelastic cross sections

Accurately determined parity-resolved state-to-state cross sections

Complemented previous studies by providing detailed experimental data

Abstract

We present an experimental study on the rotational inelastic scattering of OH ($X^2\Pi_{3/2}, J=3/2, f$) radicals with He and D$_2$ at collision energies between 100 and 500 cm$^{-1}$ in a crossed beam experiment. The OH radicals are state selected and velocity tuned using a Stark decelerator. Relative parity-resolved state-to-state inelastic scattering cross sections are accurately determined. These experiments complement recent low-energy collision studies between trapped OH radicals and beams of He and D$_2$ that are sensitive to the total (elastic and inelastic) cross sections (Sawyer \emph{et al.}, \emph{Phys. Rev. Lett.} \textbf{2008}, \emph{101}, 203203), but for which the measured cross sections could not be reproduced by theoretical calculations (Pavlovic \emph{et al.}, \emph{J. Phys. Chem. A} \textbf{2009}, \emph{113}, 14670). For the OH-He system, our experiments validate the inelastic cross sections determined from rigorous quantum calculations.