Quantum-state resolved bimolecular collisions of velocity-controlled OH with NO radicals

TL;DR

This study measures quantum-state resolved inelastic scattering cross sections for bimolecular collisions between velocity-controlled OH and NO radicals, revealing the importance of electrostatic forces in molecular interactions.

Contribution

It provides the first detailed quantum-state resolved measurements of bimolecular collisions between two open-shell molecules, combining experimental data with quantum calculations.

Findings

Measured inelastic scattering cross sections for OH-NO collisions between 70 and 300 cm$^{-1}$.

Good agreement between experimental results and quantum coupled-channels calculations.

Electrostatic forces are identified as crucial in complex molecular collision processes.

Abstract

Whereas atom-molecule collisions have been studied with complete quantum state resolution, interactions between two state-selected molecules have proven much harder to probe. Here, we report the measurement of state-resolved inelastic scattering cross sections for collisions between two open-shell molecules that are both prepared in a single quantum state. Stark-decelerated OH radicals were scattered with hexapole-focused NO radicals in a crossed beam configuration. Rotationally and spin-orbit inelastic scattering cross sections were measured on an absolute scale for collision energies between 70 and 300 cm$^{-1}$. These cross sections show fair agreement with quantum coupled-channels calculations using a set of coupled model potential energy surfaces based on ab initio calculations for the long-range non-adiabatic interactions and a simplistic short-range interaction. This comparison reveals the crucial role of electrostatic forces in complex molecular collision processes.