Observation of correlated excitations in bimolecular collisions

Abstract

Whereas collisions between atoms and molecules are largely understood, collisions between two molecules have proven much harder to study. In both experiment and theory, our ability to determine quantum state-resolved bimolecular cross sections lags behind their atom-molecule counterparts by decades. For many bimolecular systems, even rules of thumb -- much less intuitive understanding -- of scattering cross sections are lacking. Here, we report the measurement of state-to-state differential cross sections on the collision of state-selected and velocity-controlled nitric oxide (NO) radicals and oxygen (O2) molecules. Using velocity map imaging of the scattered NO radicals, the full product-pair correlations of rotational excitation that occurs in both collision partners from individual encounters are revealed. The correlated cross sections show surprisingly good agreement with quantum scattering calculations using ab initio NO-O2 potential energy surfaces. The observations show that the well-known energy-gap law that governs atom-molecule collisions does not generally apply to bimolecular excitation processes, and reveal a propensity rule for the vector correlation of product angular momenta.

arXiv commentReceived: 06 September 2017 Accepted: 20 December 2017 Published online: 19 February 2018, Nature Chemistry 2018

References in corpus (3)

• Imaging resonances in low-energy NO-He inelastic collisions
• Quantum-state resolved bimolecular collisions of velocity-controlled OH with NO radicals
• State-to-State Differential and Relative Integral Cross Sections for Rotationally Inelastic Scattering of H2O by Hydrogen

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