arXiv subjects

Mateo Londoño

Publications and source records attributed to Mateo Londoño.

9 recordsLinked to original sources

arXiv2026

Quantum Chemistry in a Novel Hybrid Dipolar Atom-Ion Mixture

Merging trapped ions with cold atomic clouds offers intriguing prospects for quantum chemistry and many-body quantum simulations. Especially when going beyond the standard alkali atomic baths by using lanthanide atoms, opportunities arise to study the interplay between the intermediate-range atom-ion interaction and the tunable long-range dipolar atom-atom interactions. However, the high total angular momentum of the ground-state of open-shell lanthanides, e.g. $^{5}I_{8}$ for dysprosium, affects the atom-ion potential. Here, we discuss the implications for long- and short-range atom-ion interactions and present a novel apparatus which combines an ytterbium ion (Yb$^{+}$) with dipolar dysprosium (Dy) atoms. We highlight the consequences of this novel Dy-Yb$^{+}$ mixture for observing buffer gas cooling, (non-) radiative charge transfer, and three-body recombination. While the energy-averaged rates are dominated by radiative charge transfer, particularly radiative association, we find that three-body recombination can compete with molecular-ion formation at Dy densities $n\gtrsim 10^{12}$ cm$^{-3}$. This competition is further enhanced by the expected non-thermal distribution of ion energies. These processes could be experimentally characterised through controlled variation of the atom-ion interaction parameters, providing a direct test of our theoretical predictions.

physics.atom-ph↗

arXiv2026

Electronic properties of the Radium-monochalcogenides RaX (X = O,S,Se) and RaO+/- ions

We present a theoretical investigation on the electronic structure and properties of radium monochalcogenides, with chalcogens O, S, and Se, as well as the ionic species RaO +/-. Our approach combines fully relativistic and partially relativistic quantum-chemistry methods. Electronic properties are obtained using the exact two-component Hamiltonian-based coupled-cluster approach with single, double, and perturbative triple excitations [CCSD(T)+ X2C], while potential energy curves are computed using an internally contracted multireference configuration interaction method, including relativistic effects through small-core pseudopotentials and Pauli-Breit operator diagonalization (MRCI+Q+ECP+SO). The dimers exhibit very large permanent dipole moments and sizable dipolar polarizabilities, while the Franck-Condon factors among the lowest electronic states are highly non-diagonal. These features are discussed in terms of the divalent character of the chemical bonding in the neutral species.

physics.chem-ph↗

arXiv2025

AlF-AlF sticking time and prospects for ultracold dimers

We report on the sticking time of the AlF dimer in the ultracold regime. We employ a full-dimensional potential energy surface for AlF-AlF, constructed using a machine learning approach [X. Liu et al., J. Chem. Phys. 159, 144103 (2023)], to compute the density of states using a semi-classical counting method. Next, using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory, we determine a sticking time of 216.3 ns, which is shorter than that of other previously reported dimers. We explain these results in light of the ratio of the dissociation energy of the complex to the dissociation energy of the molecule, yielding a computationally inexpensive scheme to estimate the sticking time of collisional complexes.

physics.atm-clus↗

arXiv2025

Rotational quenching of monofluorides in a cryogenic helium bath

Buffer gas cooling, one of the most relevant direct cooling techniques for cooling molecules, relies on dissipating the energy of the molecule via collisions with a buffer gas. The cooling efficiency hinges on the molecule-atom scattering properties, concretely, on the transport properties. This work presents a global study on the interactions, collision dynamics, and transport properties of monofluoride molecules (X-F), being X a metal, in the presence of a cold He buffer gas. The interactions are calculated using ab initio quantum chemistry methods, and the dynamics is treated fully quantal, assuming the monofluoride molecule is a rigid rotor. The resulting thermalization and rotational quenching rates are analyzed in light of the Born Distorted Wave Approximation (BDWA), yielding an explanation based on the elemental physical properties of the molecule under consideration. Therefore, the analysis of our results reveals the physics behind the rotational quenching of molecules in the presence of a cold buffer gas.

physics.chem-ph↗

arXiv2025

Ultracold long-range van der Waals Rydberg trimer

Rydberg molecules, Rydberg-atom or Rydberg-molecule, are an essential ingredient of cold molecular sciences. However, due to the richness of Rydberg-neutral interactions, new kinds of Rydberg molecules and binding mechanisms are still to be discovered. In this work, we predict the existence of ultra-long-range van der Waals trimers in dilute atom-gas mixtures. These are bound states of a Rydberg atom and a diatomic polar molecule mediated by the long-range van der Waals interaction. This new binding mechanism gives rise to trimers with sizes between 5-500~nm and binding energies between 2 MHz and 0.2 kHz depending on the atomic principal quantum number $n$ and orbital angular momentum $L$. We show that these molecules can be produced via two-photon photoassociation, with rates on the order of (10$^{-13}$ - 10$^{-11}$) cm$^{3}$s$^{-1}$ for temperatures in the range of (0.5 $μK$ - 10$μK$), and discuss the feasibility of observing trimer resonances.

physics.atom-ph↗

arXiv2024

Exploiting SU(N ) dynamical symmetry for rovibronic stabilization of a weakly bound diatomic molecule

We propose a multilevel scheme to coherently transfer the population of a diatomic molecule from a rovibrational level to a target rovibrational level of the same electronic state or another. It involves a linear chain of N rovibrational levels alternating between the initial electronic state and a second electronic state, conveniently selected according to the dipole couplings between consecutive levels. A set of N - 1 simultaneous weak laser $π$ pulses, with simple analytical shapes, each in resonance between two neighbors of the chain, transfers the population from the initial rovibronic state gradually and consecutively through the chain, until at the end of the process it resides in the target rovibronic state, as in a kind of ping-pong game between the two electronic states. Using the partial-wave expansion of the molecular wave function, vibrational bases within the J manifolds of each electronic state, and the rotating-wave approximation (RWA), we map the radial Hamiltonian to the one of a spin s = (N - 1)/2 under a static magnetic field, providing an analytical formula for the populations of the linked states. As an illustration, we apply the scheme to the stabilization into the absolute ground state of a KRb molecule initially in the high-lying $\upsilon$ = 75, J = 6 level of the ground electronic state $X^{1}Σ^{+}$. With a chain of seven rovibronic states, three of them belonging to the excited $A^{1}Σ^{+}$ electronic state, and pulses of 0.4 ns of duration, the population is fully transferred into the target state in about 1 ns.

quant-ph↗

arXiv2023

Vibrational ladder-descending photostabilization of a weakly bound molecule: Quantum optimal control with a genetic algorithm

We propose an optical control scheme for driving a polar molecule from a high-lying vibrational level to a target low-lying one, within the same electronic state. The scheme utilizes an infrared chirped laser pulse with an analytical shape, whose parameters are optimized by means of a heuristic formulation of quantum optimal control based on a genetic algorithm. We illustrate this methodology computationally for a KRb Feshbach molecule in the lowest triplet electronic state.

quant-ph↗

arXiv2023

Cold atom-ion systems in radiofrequency multipole traps: event-drive molecular dynamics and stochastic simulations

We have studied the general aspects of the dynamics of an ion trapped in an ideal multipolar radiofrequency trap while interacting with a dense cold atomic gas. In particular, we have explored the dynamical stability, the energy relaxation and the characteristic harmonic motion exhibited by a trapped Yb$^{+}$ ion in different multipolar potentials and immersed in various cold atomic samples (Li, Na, Rb, Yb). For this purpose, we used two different molecular dynamics simulations; one based on a time-event drive algorithm and the other based on the stochastic Langevin equation. Relevant values for experimental realizations, such as the associated ion's lifetimes and observable distributions, are presented along with some analytical expressions which relate the ion's dynamical properties with the trap parameters.

physics.atom-ph↗

arXiv2022

The dynamics of a single trapped ion in a high density media: a stochastic approach

Based on the Langevin equation, a stochastic formulation is implemented to describe the dynamics of a trapped ion in a bath of ultracold atoms, including an excess of micromotion. The ion dynamics is described following a hybrid analytical-numerical approach in which the ion is treated as a classical impurity in a thermal bath. As a result, the ion energy's time evolution and distribution are derived from studying the sympathetic cooling process. Furthermore, the ion dynamics under different stochastic noise terms is also considered to gain information on the bath properties' role in the system's energy transfer processes. Finally, the results obtained from this formulation are contrasted with those obtained with a more traditional Monte Carlo approach.

cond-mat.quant-gas↗