Tomography of Feshbach resonance states

Abstract

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.

Quantum stereodynamics of cold molecular collisions

“…Narrow resonances in energy-resolved cross sections from such measurements were demonstrated for Penning ionization of H 2 by He* by Narevicius and coworkers. 121–123 We expect such techniques would be extended to SARP prepared molecules in the near future.…”

Improving potential energy surfaces using measured Feshbach resonance states

“…The recoil translational energy is determined from measurements which are expected to probe large spatial areas of a PES and the underlying intermolecular interactions (28). The redistribution of energy due to the Feshbach resonances has recently been mapped out comprehensively for He − H + 2 and Ne − H + 2 with coincidence velocity map imaging of electrons and cations, yielding very favorable agreement between theory and experiment (26). In these experiments, the ionic molecular complexes are generated at separations of up to 10 a 0 between the rare gas atom and the molecular ion, confirming that the experiment indeed probes a large spatial extent of the PES, including its long-range part.…”

“…The present work uses all very high-quality experimentally measured (26) (27,28). The recoil translational energy is determined from measurements which are expected to probe large spatial areas of a PES and the underlying intermolecular interactions (28).…”

Enhanced Total Vibrational Excitation Yield in a Slow Narrow-Pulsed Hydrogen Molecular Beam

“…Similarly, in ion–molecule reactions where the ions are held in the trap, − all the molecules in the beam would react with the ions. This is also true for crossed beam experiments that do not require the detection laser, ,− where the crossed region is usually larger than the detection laser spot, necessitating the excitation of a larger portion of the beam.…”

“…Understanding the influence of internal and translational motion on chemical reactions is crucial for unraveling reaction mechanisms. − Notably, molecular vibration has been found to significantly impact the rates of gas-phase and surface reactions, making it a topic of great importance in the realm of reaction dynamics. − Particularly, hydrogen (H 2 ) stands out as a vital molecule due to its simplicity and significance in chemistry. Studies involving collisions of molecular hydrogen with other atoms or surfaces have provided valuable insights into reaction dynamics and served as tests for theoretical predictions concerning various collisional processes. − As a result, there is strong interest in developing methods capable of preparing a substantial quantity of H 2 molecules in a specific quantum state. However, high-efficiency excitation of H 2 molecules to their vibrationally excited states proves to be a challenging endeavor, especially for the high overall population in a large region.…”