Tomography of Feshbach resonance states

Feshbach resonances are fundamental to interparticle interactions and become particularly important in cold collisions with atoms, ions, and molecules. In this work, we present the detection of Feshbach resonances in a benchmark system for strongly interacting and highly anisotropic collisions: molecular hydrogen ions colliding with noble gas atoms. The collisions are launched by cold Penning ionization, which exclusively populates Feshbach resonances that span both short- and long-range parts of the interaction potential. We resolved all final molecular channels in a tomographic manner using ion-electron coincidence detection. We demonstrate the nonstatistical nature of the final-state distribution. By performing quantum scattering calculations on ab initio potential energy surfaces, we show that the isolation of the Feshbach resonance pathways reveals their distinctive fingerprints in the collision outcome. Description Imaging all Feshbach resonances at once Quantum scattering resonances, and Feshbach resonances in particular, are the key features of cold collisions that can fundamentally change collision outcomes. Numerous previous experiments have mainly focused on the initial channel, providing limited insight into the resonant scattering dynamics. Margulis et al. developed a method in which the energetics and decay channels of Feshbach resonances, formed by collisions induced by Penning ionization of metastable helium or neon atoms and the ground-state hydrogen molecule, were mapped out by ion-electron coincidence velocity map imaging with a precision of several Kelvin, enough to resolve all the final rovibrational quantum states in a single measurement. The proposed method offers a new approach to quantum state mapping of resonant collision dynamics. —YS Feshbach resonances in reaction complexes of H2+ ions and rare gas atoms are resolved in a tomographic manner.