Merged-beams experiments in atomic and molecular physics

Abstract

The merged-beams technique is powerful for the experimental study of certain classes of atomic and molecular processes that cannot be as readily or accurately addressed by other methods. The principal advantages of the technique are the ability to make quantitative studies of collisional interactions with high resolution at low relative energies, to collect products that have undergone appreciable angular scattering, and to investigate processes involving short-lived or chemically-reactive species. Despite continuing advances in ion-source and particle-beam technologies, merged-beams experiments remain a challenge, constituting a relatively small but growing fraction of the worldwide effort in atomic and molecular collisions research. This review outlines the fundamental principles of the merged-beams method, reviews techniques and progress, and focuses on three active programs to highlight the advantages of the method for addressing fundamental questions in atomic and molecular physics.

Spectroscopic experiments on autoionization and neutral fragmentation in the high-Rydberg states of BH

“…Work in storage rings, where cooled ions collide with mono-energetic electrons, can reveal structured cross sections that reflect the underlying physics [1]. Laser spectroscopy offers similar information, in some cases with superior precision and state specificity [2] The present work reports multiphoton spectroscopic results for BH that characterize scattering resonances formed by high-lying Rydberg transients strongly coupled to decay channels for electron loss and bond cleavage to neutral atoms.…”

“…Spectroscopic experiments on autoionization and neutral fragmentation in the high-Rydberg states of BH 1. Introduction When a molecular cation and an electron combine, the potential energy present initially in Coulomb attraction dissipates in the relaxation of the energized system along a complex path of transient electronic configurations.…”

“…Our results show that, when energetically accessible, electron loss dominates detectable neutral fragmentation. 1 To whom any correspondence should be addressed Figure 1 shows an energy-level diagram. Final excited states are produced by stepwise absorption of photons from three lasers.…”

Experiments with Highly-Ionized Atoms in Unitary Penning Traps

“…On the other hand, there is far less information available for electron capture at low energy, with the bulk of the experimental data coming from merged-beams experiments [51,52]. Understanding the low-energy regime is likely to become important for proposed applications, including atomic clock development, quantum information processing and precise tests of fundamental theory.…”

Three-body Reaction Dynamics in Dissociative Recombination

“…A review on the use of merged-beams in atomic and molecular physics has recently been published. [7] …”