Tomography of Feshbach Resonance States

Abstract

Feshbach resonances are fundamental to interparticle interactions and have been detected in collisions with atoms, 
ions, and molecules. However, extracting the resonance contribution to the collision dynamics and identifying their 
effect on the collision outcome has remained elusive. Here we present the detection of Feshbach resonance states 
with complete final quantum state resolution in a benchmark system for strongly interacting and highly anisotropic 
collisions -- molecular hydrogen ions colliding with noble gas atoms. We launch the collisions by cold Penning 
ionization which allows us to exclusively populate Feshbach resonances that span both short- and long-range parts of 
the interaction potential. We simultaneously resolve all final molecular channels of the Feshbach resonances in a 
tomographic manner using ion-electron coincidence velocity map imaging. Despite the strong mixing of all the 
degrees of freedom during the collision, we do not observe a statistical distribution of the final quantum states. 
We demonstrate that isolation of the Feshbach resonance pathway enables the detection of unique fingerprints of the 
resonant dynamics as confirmed by full \textit{ab initio} quantum scattering calculations.