arXiv subjects

Baruch Margulis

Publications and source records attributed to Baruch Margulis.

5 recordsLinked to original sources

arXiv2025

Feshbach Resonances in Cold Collisions: Benchmarking State of the Art ab initio Potential Energy Surfaces

High-quality potential energy surfaces (PES) are a prerequisite for quantitative atomistic simulations, with both quantum and classical dynamics approaches. The ultimate test for the validity of a PES are comparisons with judiciously chosen experimental observables. Here we ask whether cold collision measurements are sufficiently informative to validate and distinguish between high-level, state-of-the art PESs for the strongly interacting Ne-H$_2^+$ system. We show that measurement of the final state distributions for a process that involves only several metastable intermediate states is sufficient to identify the PES that captures the long-range interactions properly. Furthermore, we show that a modest increase in the experimental energy resolution will allow for resolving individual Feshbach resonances and enable a quantitative probe of the interactions at short and intermediate range.

physics.chem-ph↗

arXiv2025

High-fidelity quantum state control of a polar molecular ion in a cryogenic environment

We use a quantum-logic spectroscopy (QLS) protocol to control the quantum state of a CaH+ ion in a cryogenic environment, in which reduced thermal radiation extends rotational state lifetimes by an order of magnitude over those at room temperature. By repeatedly and adaptively probing the molecule, detecting the outcome of each probe via an atomic ion, and using a Bayesian update scheme to quantify confidence in the molecular state, we demonstrate state preparation and measurement (SPAM) in a single quantum state with infidelity less than 6x10^-3 and measure Rabi flopping between two states with greater than 99% contrast. The protocol does not require any molecule-specific lasers and the detection scheme is non-destructive.

physics.atom-ph↗

arXiv2023

Tomography of Feshbach Resonance States

Feshbach resonances are fundamental to interparticle interactions and become particularly important in cold collisions with atoms, ions, and molecules. Here 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 exclusively populating 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 non-statistical 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.

physics.atom-ph↗

arXiv2022

Observation of the P-wave Shape Resonance

Partial wave resonances are quasi-bound states that are formed by tunneling through the centrifugal barrier. Such states are important to collisions that deviate from the Langevin limit where direct collision path is suppressed due to quantum symmetry or a potential barrier. In such a case, quantum resonances play a major role in the dynamics at low temperatures where scattering process can be described mainly by the resonance contribution. Here we present the first observation of the lowest-lying partial wave resonance in the Penning ionization collisions between metastable neon and rovibrationally ground state HD molecules. We observe the resonance at an energy of $k_B\times$22mK taking advantage of the phase space correlation similar to atomic delta kick cooling. We show that the $p$-wave resonance position is particularly sensitive to the leading term of the van der Waals interaction. We also measure shape resonance at a higher angular momentum state, $l=6$, allowing us to disentangle and probe the short and the long parts of the intermolecular interaction.

physics.atom-ph↗

arXiv2020

Direct Observation of a Feshbach-resonance by Coincidence-detection of Ions and Electrons in Penning Ionization Collisions

Observation of molecular dynamics with quantum state resolution is one of the major challenges in chemical physics. Complete characterization of collision dynamics leads to the microscopic understanding and unraveling of different quantum phenomena such as scattering resonances. We present a new experimental approach for observing molecular dynamics involving neutral particles and ions that is capable in providing state-to-state mapping of the dynamics. We use Penning ionization reaction between argon and metastable helium to generate argon ion and ground state helium atom pairs at separation of several angstroms. The energy of ejected electron carries the information about the initial electronic state of an ion. The coincidence detection of ionic products provides a state resolved description of the post-ionization ion-neutral dynamics. We demonstrate that correlation between the electron and ion energy spectra enables us to directly observe the spin-orbit excited Feshbach resonance state of HeAr$^+$. We measure the lifetime of the quasi-bound HeAr$^+$ A$_2$ state and discuss possible applications of our method.

physics.atom-ph↗