Molecule-molecule scattering

The measurement of state-to-state cross sections for collisions between atoms and molecules has been imperative to our current understanding of molecular interactions. Yet, in most natural environments, energy tranfer between two molecules is of relevance. The precision that state-resolution that can be achieved using a Stark decelerator allows for the measurement of state-to-state cross sections for collisions between two state-selected beams. We have recently demonstrated this by scattering Stark-decelerated OH radicals with hexapole state-selected NO radicals. Read here our paper Quantum state-resolved bimolecular collisions of velocity controlled OH with NO radicals in Science.


Experimental setup to study inelastic scattering between Stark-decelerated OH radicals and hexapole state-selected NO radicals. From Kirste et al., Science 338, 1060 (2012).

The perfectly controlled and well-defined packets of Stark-decelerated OH radicals allows for the measurement of absolute state-to-state scattering cross sections as a function of the collision energy. The measured cross sections agree well with a theoretical model for radical-radical collisions based on ab initio calculations of the long-range nonabiabatic interactions. This experiment epitomizes the level of control and precision that can be reached nowadays in crossed beam scattering experiments, and revealed the crucial role of electrostatic forces in complex molecular collision processes.


Absolute state-to-state inelastic scattering cross sections for OH in collisions with NO radicals. The solid lines are the theoretically predicted cross sections. From Kirste et al., Science 338, 1060 (2012).